Asian J. Arts Cult. 2026; 26(2): 81

Morragotwong Phumplab

Department of Asian Studies, Faculty of Liberal Arts, Thammasat University, 10200, Thailand

(Corresponding author’s e-mail: morragotwong.p@arts.tu.ac.th)

Received: 3 May 2025, Revised: 17 November 2025, Accepted: 20 November 2025, Published: 27 November 2025

Abstract

This article investigates the eastern coastline of the Gulf of Siam as a historically significant maritime space that shaped the political and economic dynamics between Siam and Vietnam from the late eighteenth to mid-nineteenth centuries Following the fall of Ayutthaya in 1767, the emerging Siamese state (Thonburi and early Bangkok) and the Nguyễn regime in Vietnam competed for influence over this strategic sea space, particularly focusing on key ports such as Chanthaburi and Hà Tiên. The region became a dynamic zone of interaction marked by naval warfare, commercial expansion, and population mobility. Central to this transformation were overseas Chinese migrants, including Cantonese, Teochew, and Hokkien groups, who established influential littoral communities, contributed to maritime trade, shipbuilding, and local governance, and served as intermediaries between local rulers and broader transregional networks. Drawing on diverse historical sources—maps, chronicles, travelogues, and oral histories in Thai, Vietnamese, French, and English—this study highlights how both Siamese and Vietnamese polities projected power across the Gulf and secured economic resources, particularly during the interregnum between older kingdom collapse and colonial encroachment. Conceptually, the article integrates the frameworks of the water frontier and hydrarchy. While the water frontier emphasizes the Gulf’s fluidity, interconnectedness, and strategic importance, hydrarchy highlights the ways maritime power was organized, negotiated, and contested both from above, through state authority, and from below, through the mobility and autonomy of seafarers, migrants, and coastal communities. By linking these two frameworks, the study challenges land-centric national historiographies that have long marginalized the maritime dimension of state-building. It foregrounds the agency of littoral communities and transnational actors, reinterpreting the eastern Gulf of Siam as a dynamic arena of regional integration, political negotiation, and historical mobility.

Keywords: Water frontier, Hydrarchy, Gulf of Siam, Littoral communities, Siam, Vietnam, Chanthaburi, Hà Tiên, Overseas Chinese, Maritime Southeast Asia

Introduction

The sea space on the east coastline of the Gulf of Siam, which connected between Thailand and Vietnam, has been a significant sea unit. It reflected the political, economic, and social interaction between the regional and international states, merchants, and local inhabitants. Since the fall of Ayutthaya in 1767, Thonburi and Bangkok attempted to restore and expand their political and economic power. The eastern coast of the Siamese Gulf became the first choice for new Siamese rulers who sought to control the prosperous regional ports, particularly Chanthaburi and Hà Tiên. Between the 1760s and the 1840s, Siam and Vietnam had contested over this sea space politically and economically. Several naval warfares exploded over the Siamese and Vietnamese sphere of influence.

The concept of “water frontier” or the land that remained to the enormous underwater or in the swamps significantly showed the dynamic political interaction and commercial expansion among the political centers along the coastline of Mekong Delta to the Gulf of Siam, and in the west and east coastlines down to the south of Malay Peninsula. These areas were a backwater and a deserted coast where had been changed to be the prosperous economic kingdoms and political centers in mainland Southeast Asia, namely Thonburi and Bangkok of Siam and the Nguyễn of Vietnam (Li, 2004). This perspective challenges the territorial orientation of Southeast Asian historiography, situating the Gulf of Siam as a fluid zone where imperial projection, commerce, and migration intersected.

Building upon this notion of the water frontier, the study further incorporates the concept of “hydrarchy” to explore how authority and agency were structured across maritime networks extending beyond the direct reach of centralized states (Linebaugh & Rediker, 2000). The framework of hydrarchy illuminates not only the ways in which Siamese and Vietnamese rulers projected sovereignty across the sea, but also how seafarers, Chinese junk traders, and littoral communities constituted networks that both supported and contested imperial power. In this sense, the Gulf of Siam represents a dual domain of governance, where imperial ambitions coexisted with a sea-based social order shaped by its own patterns of exchange, mobility, and negotiation.

Since the seventeenth century, the junk trade that sailed from Southern China, mainly from Fujian and Guangdong to the Gulf of Siam, had significantly been increasing and was defined as “the Chinese Century” (Sakurai & Kitagawa, 1999; Li, 2004; Reid, 2004). Siam and Vietnam sent tribute missions to the Qing court every year to keep cordial relations and commercial benefits with China. The Chinese migrants in different ethnic groups – i.e., Cantonese, Teochew, and Hokkien – sailed from South China and settled down in the vital regional ports along the South China Sea and the Gulf of Siam. The political and economic circumstances in the area were strongly influenced by these overseas Chinese. Not only were the Chinese involved in the political transition along the Gulf of Siam, but the local and regional mobility that underpinned this hydrarchical water frontier.

Research objectives

1. To examine how Vietnamese and Siamese rulers projected and utilized the eastern coastline of the Gulf of Siam as a strategic space for political and economic expansion between the 1760s and 1840s.

2. To explore the significance of this maritime space for littoral communities, particularly migrant groups such as overseas Chinese and Vietnamese, in shaping patterns of settlement, trade, and regional influence.

3. To analyze how the eastern Gulf of Siam functioned as a site of regional and international interaction, reflecting the interconnected political and economic relationships between Siam (Thonburi and Bangkok) and Vietnam (Huế).

Research framework

This study adopts a qualitative historical approach to examine the eastern coastline of the Gulf of Siam as a maritime frontier between the 1760s and 1840s. Utilizing a multilingual approach and drawing from a wide range of historical sources at both local and regional levels, the research engages with materials in Thai, Vietnamese, French, and English. Through textual and cartographic analysis, the study investigates how Siamese and Vietnamese rulers projected power across this strategic sea space, and how maritime and littoral regions became arenas for political contestation, commercial integration, and regional mobility.

Essential primary sources include official chronicles and annals produced by both Siamese and Vietnamese courts, such as Phraratchaphongsawadan Krung Si Ayutthaya (Ayutthaya Chronicle), Phraratchaphongsawadan Krung Thonburi (Thonburi Chronicle), Phraratchaphongsawadan Krung Kampucha (Cambodia Chronicle), Phraratchaphongsawadan Ratchawong Ching (Qing Silu) and Phraratchaphongsawadan Krung Rattanakosin (Rattanakosin Chronicle), as well as the Vietnamese Đại Nam Thực Lục (Veritable Records of Đại Nam), Gia Định Thành Thông Chí (Gazetteer of Gia Định Citadel), Mạc Thị Gia Phả (Annals of the Mạc Family), and Đại Nam Nhất thống chí (Unified gazetteer of the Great South). These internal records reveal precise information about regional governance, tribute relations, warfare, and port networks. Cartographic materials also play a crucial role. These include historical maps commissioned by both polities that reflect state perceptions of maritime landscape. The royal Siamese maps depict maritime routes, port towns, and regional linkages from the Gulf of Siam to the Mekong Delta.

To broaden the analytical lens, the study integrates Western travel literature and diplomatic reports that provide outsider perspectives on the region’s maritime and political dynamics. These include George B. Bacon’s Siam: The Land of the White Elephant As It Was and Is, which offers rich commentary on nineteenth-century Siamese society; Michael Smithies’ edition of Alexander Hamilton: A Scottish Sea Captain in Southeast Asia, which is a firsthand account of early modern maritime trade; John Crawfurd’s Journal of an Embassy to the Courts of Siam and Cochin China, which provides diplomatic insights into regional geopolitics; and George Finlayson’s The Mission to Siam and Huế 1821-1822, which details cultural, commercial, and naval observations. These works serve as intermediary narratives, contextualizing how external observers observed, navigated, and interpreted Southeast Asian marine area, while also adding a valuable comparative dimension to indigenous archives.

Theoretically, the research is informed by maritime history and borderland studies, specifically the concept of the “water frontier” and “hydrarchy.” These approaches move away from land-centric views of sovereignty and instead view the sea as a dynamic, connecting, and contested area. This methodology, which combines official documents, geographical data, and Western outsider perspectives, provides a comprehensive and layered picture of regional interaction, state formation, and the political economy of early modern Southeast Asia.

The water frontier first articulated by Tana (2004), redefines the sea as a connective and dynamic zone of interaction, challenging land-based narratives of state formation. It highlights how the coastlines of the Mekong Delta and the Gulf of Siam became arenas of political expansion and commercial exchange linking Siam, Vietnam, Cambodia, and Southern China through the continuous circulation of people, goods, and ideas. Traditionally viewed as marginal backwaters, these maritime spaces were, in fact, integral frontiers of state power and regional integration, where mobility and exchange shaped both political and economic landscapes.

While the notion of the water frontier captures the geographical fluidity and economic interconnectivity of maritime Southeast Asia, it is primarily spatial and descriptive. To address how authority, order, and agency operated within such fluid frontiers, this study turns to Linebaugh and Rediker’s (2000) concept of “hydrarchy.” Hydrarchy theorizes the organization of power on and through the sea, encompassing two intertwined structures: governance from above, imposed by states and empires seeking to control maritime routes and labor, and organization from below, formed by seafarers, traders, and littoral communities who established autonomous systems of cooperation, exchange, and resistance.

By integrating these two frameworks, the study moves beyond geography to examine the politics of maritime interaction. If the water frontier describes the patterns of movement and connection that shaped the Gulf of Siam, hydrarchy reveals how these movements were governed, contested, and socially organized. Together, they illuminate the sea not simply as a passageway, but as a political and social process—a fluid arena where imperial ambition, commercial exchange, and community autonomy intersected.

Physical geography of the Gulf of Siam and its maritime routes

Geographical characteristics and climate of the east coast of the Gulf of Siam have benefited seafarers and vessels for a long time. The Gulf connects to the South China Sea/East Sea (Biển Đông) and the Pacific Ocean. This region was famously known as the convenient and safe route for maritime en route. Most of the coastal areas along the Gulf are shallow inlets. The coastline of the west shore is from Southern Thailand to the end of the Malay Peninsula, and the east coast is from the east of Thailand down to Cambodia and South Vietnam. The northernmost of the Gulf called “Pak Nam (the river mouth)” is the bay of Bangkok that connects to Chaophraya River. The southernmost of the Gulf is at Kota Baru where lies on the Malay coast. The southeastern-most located at the end of Cà Mau peninsular in Vietnam. Along the shore of the Gulf in the east coastline, there are large luxuriant islands and small islets, for examples, Ko Chang, Ko Sichang, Ko Samae San, Ko Mak, Ko Kut, Ko Phai, Ko Khram located in Thailand, Koh Kong, and Koh Rong in Cambodia and Phú Quốc island in Vietnam. These islands and islets have been the shelters for the seafarers and vessels since the prosperous era of maritime trade.

From north to south, the Gulf measured 800 kilometers and from east to west 560 kilometers. Its surface is around 320,000 square kilometers (World Atlas, 2022). The Gulf consists of lucrative fishing grounds. The shallow inlet results to the water exchange being slow and the healthy water flow from the rivers reduce the salinity in the Gulf as well as enrich sediments, particularly in the estuaries. In the seventeenth century, the European traveler recorded that “Siam Bar is only a large bank of soft mud and, at spring tide, not above ten or eleven-foot water on it” (Smithies, 1997, pp. 180-181). Muddy areas and a confluence of salt and freshwater make the shore areas on the eastern coast have abundant mangroves. These mangrove forests benefit from the reduction of the coastal erosion.

Most of the year, two monsoon winds influence the Gulf. Between November and April, the northeast monsoon prevails, bringing dry and stable conditions with wind speeds typically ranging from 5 to 20 knots. This period is characterized by clear skies and minimal rainfall, making it favorable for maritime activities. Conversely, from mid-May to mid-October, the southwest monsoon dominates, ushering in the wet season with increased rainfall and variable wind patterns. During this time, the region experiences frequent and heavy showers, particularly in August and September, which are typically the wettest months. During the monsoon season, the rain copiously showers almost every day. The tropical storms in the Gulf develop from the tropical disturbance in the low-pressure region, which occurs between November and lower probabilities in early December (Climatological Group, 2015; McDonald, 1999).

Maritime routes along the eastern coast of the Gulf were regionally and internationally significant for economic and political activities. European historical travelogues mentioned that the sea routes from Siam to South Vietnam started from Pak Nam (now located in Samutprakarn province). Paknam was the first point for vessels and junks to anchor before sailing to Chaophraya River or connected to inland Bangkok. Alexander Hamilton, the Scottish captain who traveled to the Gulf in the early seventeenth century, wrote that “It is easy getting onto it in the southwest monsoons, because it two or three tides, with the motion the ship receives from the small waves and the assistance of the wind” (Smithies, 1997, pp. 180-181). The northeast monsoon was the time for coming out because the sea is being smooth (Smithies, 1997).

From the Siamese and Vietnamese sources, regional seafarers also sailed along the Gulf using the same maritime routes as the Europeans. The most explicit Vietnamese reference is the collected records of itineraries to Siam (Xiêm La Quốc: Lộ trình tập lục), compiled by Tống Phước Ngoạn, a senior mandarin of the Nguyễn court in Hà Tiên (Phạm, 2017). The account recorded about the naval routes in the whole Gulf of Siam in 1810 during the reign of Emperor Gia Long, which significantly portrays the geographical information and connections of sea space in the region. More importantly, it reveals how Siam, Vietnam, and Cambodia connected through the water frontier. For the coastal routes, it linked from the mouth of the lower Mekong branch to Bassac River and passed through Rạch Giá, Hà Tiên, Rean, Koh Kong, Laem Sing cape (Chanthaburi), Ko Khram, Ko Lan, Ko Sichang, Bang Plasoi (Chonburi) up to Pak Nam (Phạm, 2017). Tống Phước Ngoạn described the distance from place to place, local products and inhabitants, the location of freshwater, the depth and width of river mouths, and geographical landscapes. This record implies that the Nguyễn court was familiar with and used this sea route.

Regarding the Siamese court, the land routes were the main maps recorded during the Thonburi and the early Rattanakosin era. However, the sea route maps were the maritime routes to Southern China ports, which were the biggest trading partner. The local sea maps also portrayed the regional ports along the east coast of the Gulf. Another route was the inlets from the Mekong River branches to the Gulf of Siam during the war between Siam and Vietnam during the reign of Emperor Minh Mang and King Rama III.

Consequently, the routes from Bangkok to Southern Vietnam featured identical stops and were utilized for travel by both local sailors and Europeans. The initial stop from Paknam was Bang Plasoi, currently situated in Chonburi. In the late seventeenth century, it was abundant with agala, sappan wood, and elephant tusks. The second stop was Koh Si Chang (currently in Chonburi), where Europeans called Dutch Islands because there were Dutch stores during King Narai of Ayutthaya period. Koh Chang, a large island with lofty peaks, was also another stop (Bacon, 2000). When sailing through these islands, the ships were forced to stop because of the southwest monsoons (Smithies, 1997). The geographical characteristics of Sattahip were suitable for ships to stop by. Along the coast, there were many bold islands, with rock bases and covered with abundant vegetation. When the voyagers saw Koh Nom Low located near the entrance into the mouth of Chantabun river, it meant they already reached Chanthaburi, the important port of Siam in the late seventeenth century (Bacon, 2000).

Chanthaburi extensively consisted of the mountainous area and able to extend out to the sea and embraces the harbors. It is situated at the head of the Gulf and marked as the first territory under the control of Siam. It was well-known in the 1820s as one of the most prosperous and wealthiest provinces in Siam. Geographically, it has fertile valleys and plains. Furthermore, its geographical advantages were the convenient harbors and well protected by numerous big and small islands in the front of the province. The river mouth of Chanthabun river safely navigated for small vessels. There were thick forests and mangroves. Most of the travelers similarly recorded that Chanthaburi was a suitable port for maritime commerce (Crawfurd, 1828; Finlayson, 1988; Bacon, 2000).

Figure 1 The Gulf of Thailand.
Source: Adapted from Google Earth (2024).

Figure 2 Siamese map depicting the maritime corridor from the Malay Peninsula to Vietnam, highlighting the Siamese coast, the mouth of the Chao Phraya River, Chanthaburi, Cambodia, and adjacent coastal territories.

Source: Phasuk and Stott (2004, p. 166)

From Chanthaburi, maritime routes extended southeast toward the Cambodian ports of Kampot and Kampong Som, both of which were under Cambodian influence. Foreign and regional vessels usually sailed down to the significant port polity known as Hà Tiên ruled by the Mạc family, the overseas Chinese who had established this town in the late sixteenth century. Beyond the formal political boundaries of Siam and Vietnam, this maritime route reveals a broader web of interaction that connected numerous small ports along the Gulf of Siam. These interactions extended beyond the Siamese–Vietnamese rivalry to include a chain of smaller Cambodian ports—Kampot and Koh Kong among them—that connected with inland centers such as Phnom Penh and reached further south to the major Vietnamese port of Hà Tiên.

Hà Tiên had a deep but narrow river that connected to Bassac (or Giang Thành) river, a branch of the Mekong River. The Southwest monsoons usually brought the rainy season to town. Down to southeast of Hà Tiên were abundant mangrove forests, known as Cà Mau point. These mangrove forests vitally protected the shores from sea erosion and storms (Barrow, 1806; Smithies, 1997; Brocheux, 1995). Several islands faced with the town of Hà Tiên with several uninhabited islands. Among them, Phú Quốc was the right place for settlement, which was abundant with woods and freshwater, as well as the black and flat ground soil. This island was a safe harbor in the rainy and windy seasons (Smithies, 1997). From Hà Tiên down to the Cà Mau point, this area widely opened to the southwest monsoon impeded maritime activity in the Gulf because of the violent storms, while the northeast wind brought the cool and dry period.

These interconnected movements reflect a regional maritime dynamism that bound together the coastal zones of mainland Southeast Asia. While conventional historiography of mainland Southeast Asia has largely emphasized land-based routes and territorial power structures, particularly the expansion of royal authority toward the Gulf of Siam during the interregnum periods of both Siam and Vietnam through naval warfare (Eoseewong, 1986; Phumplab, 2010 ; Vu, 2012 ; Kanparit, 2017), other studies have focused on the economic dimension, highlighting competition over natural resource exports and control of maritime trade routes along the Gulf (Rungswadisab, 1995). These perspectives underscore the sea as a crucial arena of political and economic expansion. This study proposes that the Gulf of Siam’s maritime sphere constituted more than a site of commercial and political expansion; it operated as a dynamic network facilitating the movement of people, the exchange of ideas, and the negotiation of authority among the littoral societies of Siam, Cambodia, and Vietnam. Within this broader framework, the waterways of the Gulf exemplify a form of hydrarchy, characterized by a maritime order maintained through the interactions between rulers and littoral communities, where negotiation, refuge, and resistance to state authority were ongoing processes.

Regional interregnum, political restoration and power expansion of Siam and Vietnam in the gulf of Siam

Between the 1760s and the 1770s, political chaos emerged in mainland Southeast Asia. The warfare between Burmese and Ayutthaya Kingdoms led to the fall of Ayutthaya in 1767. The rise of the Tây Sơn movement against the Nguyễn in 1770 forced the Nguyễn family moving to Southern Vietnam. In Siam, the political turbulence brought Taksin, the future influential Siamese leader, to the east coast of the Gulf for a political restoration. While in Vietnam, the Nguyễn family and supporters used the same route to Siam for political asylum, i.e., Tôn Thất Xuân (Nguyễn Ánh’s uncle) and Mạc Thiên Tứ in 1777 and Nguyễn Ánh (later emperor Gia Long) in 1782. As mentioned earlier, the coastal route from Bangkok down to Chonburi, Rayong, Chanthaburi, Trat, Kampot, and Hà Tiên was significant, especially to the regional leaders. The east coast of the Gulf was a familiar route and a political base for Siamese and the Nguyễn rulers.

This sea space and coastal ports were strategic points for a power restoration of the Siamese led by Taksin. Only a week before Ayutthaya collapsed in April 1767, Taksin and more than 500 Siamese troops headed to the eastern coast of Siam. To collect the war vessels and gather more forces, he moved from Ayutthaya to Nakhon Nayok down to the coastal line at Chao Lo estuary, Ban Naklue, and Na Jomtien (currently in Chonburi), Rayong, Chanthaburi, and ended at Trat. Taksin used the sea route and moved his troops to recapture Ayutthaya from the Ava troops (Eoseewong, 1986; Kanparit, 2017).

Taksin was a Teochew descent. Rather than joining the other Chinese ethnic groups, he selected this route as a strategic plan because of his connections with Teochew merchants in Rayong and Chanthaburi. Taksin seized Rayong in July 1767, gathered troops, and then proceeded to Chanthaburi to negotiate with the local governor, but was unsuccessful. He executed a successful attack on Chanthaburi overnight (Bradley, 2008; Eoseewong, 1986).

In Chanthaburi, Taksin received crucial supported by Chin Chiem, a prominent Chinese merchant who held considerable influence among the local junk traders (Phraratchaphongsawadan Krung Thonburi Chabap Phanchanthanumat, 2019). The cooperation with the Teochew network was crucially economic support for establishing Taksin power. Taksin benefited from the international port of Chanthaburi, especially the increased capacity of navy troops from building more than 100 warships. He appointed the Teochew to control strategic towns on the east coast. The Teochew network became closer after the marriage between Taksin and Chin Chiem’s daughter. Taksin appointed Chin Chiem as Luang Phiphit (Phraratchaphongsawadan Krung Thonburi Chabap Phanchanthanumat, 2019). He was responsible for controlling all towns and ports along the east shoreline of the Gulf, which made enormous profits for Thonburi through the Teochew junks. In the broader Southeast Asian context, marriage and kinship alliances often functioned as strategic instruments for expanding both political influence and economic networks. Consequently, women frequently played significant—though often understated—roles in facilitating political mobility and alliance-building among competing centers of power.

Sea of Rivalries: Teochew and Cantonese Influence on the Political Struggles along the Eastern Gulf of Siam

Since the seventeenth century, there has been an influx of Chinese refugees migrating to Southeast Asia. Chinese from various ethnic groups, including Teochew, Cantonese, and Hokkien, established settlements along the coastline of Vietnam and the Gulf of Siam. They utilized distinct dialects and built commercial networks through ethnic connections, navigating junks between Southeast Asia and China. The Teochew established themselves along the eastern coastline of Siam and migrated to the northern towns of Ayutthaya, whereas the Cantonese settled in coastal towns and the Mekong delta region in southern Vietnam. The maritime domain served as a water frontier, akin to the regional commercial cohesion observed among Mediterranean coastal communities (Li, 2004). The wealth of Chinese littoral communities was essential for the restoration of power among local rulers in Siam and Vietnam. However, the naval conflict between Siam and Vietnam over the eastern shoreline of the Gulf began during the late Ayutthaya period. The primary regions of naval contestation were Chanthaburi and Hà Tiên, which were influenced by two ethnic Chinese groups: Teochew and Cantonese.

Hà Tiên was established by Mạc Cửu , a Cantonese who sought asylum in Cambodia during the late seventeenth century. The Cambodian King granted Mạc Cửu the new land near Banteay Meas, which was a Cambodian port, in exchange for him managing maritime trade (Quốc Sử Quán Triều Nguyễn, 2006; Vũ, 2006). However, Mạc Cửu began paying tribute to the Nguyễn lord in 1708. Mạc Cửu was one of the few successful Chinese immigrants who established his power through the port polity in Hà Tiên. He possessed a thorough understanding of regional politics and played a significant role in the inter-state relations among Siam, Vietnam, and Cambodia. Hà Tiên emerged as a tripartite tributary state of Ayutthaya, the Nguyễn, and Cambodia. More recent studies have reinterpreted the Mạc family as an autonomous port polity sought to balance regional authority through negotiations with surrounding local powers (Hang, 2025). Mạc Cửu introduced the Chinese cosmology and administrative system from the Ming dynasty, as evidenced by the architectural style. Following the 1770s, the Mạc rulers successfully extended their influence from the eastern coast of the Gulf to the southern tip of the Cà Mau peninsula.

Prior to the fall of Ayutthaya, Mạc Thiên Tứ, who succeeded Mạc Cửu in 1735, seized the opportunity to expand his power by occupying islands in the Gulf of Siam, such as Ko Kong, Ko Kut, and Ko Khram, in order to gain control over key maritime trade routes. The son of Mạc Cửu and a local Vietnamese woman, Mạc Thiên Tứ represented a creole or mixed-heritage figure, embodying the cultural hybridity that characterized many coastal elites of the early modern South China Sea world. In 1769, Hà Tiên established a navy fleet comprising 100 warships to seize Chanthaburi, seeking support from Siam. However, this endeavor failed as they were defeated by Siamese forces commanded by Luang Phiphit (Tan Liang in Chinese or Tran Lien in Vietnamese), the Teochew general governing Chanthaburi, who maintained close ties with Taksin (Sakurai & Kitagawa, 1999). Chanthaburi was not successfully conquered by the Vietnamese and was governed by a man of Chinese descent, appointed by the Siamese king, as noted by Finlayson in the 1820s (Finlayson, 1988).

Both Taksin and Mạc Thiên Tứ relied heavily on the collaboration of overseas Chinese networks to consolidate and expand their power (Sakurai & Kitagawa, 1999). As Creole elites of mixed Chinese and local descent, they represented a new socio-political formation in which legitimacy was derived less from royal lineage than from transregional trade and diasporic alliances. Their rise signaled a significant shift in regional political dynamics, as authority in several mainland kingdoms began to move away from hereditary nobility toward new elites whose legitimacy was rooted in commercial wealth, maritime connections, and Chinese clan networks.

Both entities represented significant potential in the region during the interregnum period along the Gulf. Thai records indicate that the conflict between Taksin and Mạc Thiên Tứ intensified when Chao Sri Sang and Chao Chui, royal descendants of Ayutthaya, sought refuge in Hà Tiên. In 1771, shortly after Taksin’s coronation, he led naval forces from Thonburi to Hà Tiên, deploying 300 warships and 15,000 fleets (Bradley, 2008). Considering the geographical location of Hà Tiên, the town is situated facing the bay. This port was primarily established as a trade hub and likely did not aim to address maritime threats. Taksin selected the highest hill that provided a comprehensive view of the town from the east and launched an attack from two sides using cannons and firearms. Taksin successfully conquered Hà Tiên and appointed Chin Chiem, a Teochew, as Phraya Rachasetthi Chin, the new governor. Mạc Thiên Tứ fled Hà Tiên and sought assistance from the Nguyễn. Subsequently, Taksin returned to Hà Tiên for the Mạc descendant and reestablished relations with the Nguyễn (Sakurai & Kitagawa, 1999).

These rivalries illustrate how the Gulf functioned as more than a water frontier of trade. It became a hydrarchical zone, where overlapping commercial and ethnic networks exercised maritime authority alongside, and sometimes against, formal state power. The interactions between Teochew and Cantonese trading networks, port polities such as Hà Tiên, and regional powers exemplify a hydrarchical order in which authority was fluid, negotiated, and shared between rulers and maritime actors. The Mạc family’s administration of Hà Tiên, for instance, reflected both state allegiance and sea-based autonomy, embodying the hybrid sovereignty characteristic of hydrarchy.

Similarly, the rivalry between Teochew and Cantonese networks within the Siamese–Vietnamese maritime sphere exemplified the coexistence of imperial control and maritime autonomy. Both Taksin and the Mạc family relied on seaborne Chinese networks whose mobility and maritime knowledge often exceeded the reach of state regulation. These networks functioned as hubs of a bottom-up hydrarchy, redistributing power through ports, islands, and trading fleets rather than fixed territorial centers.

Navigating Exile: The Nguyễn and Political Asylum Routes in the Gulf of Siam”

The east coast of the Gulf was not only important to Siam but also for Vietnam as a local route for political and religious asylum. Before the Nguyễn family escaped to Siam, this route was regularly used by the French missionaries and the Catholic Cochin Chinese for taking refuge from the religious persecution from King Phetracha of Ayutthaya (1688-1703), and also from the Nguyễn lords in the seventeenth century. Local Cochin Chinese regularly traveled along the maritime routes of the Gulf’s eastern coast.

The emergence of the Tây Sơn movement in the 1770s forced the Nguyễn family retreat down to Gia Định (Saigon) and Mekong Delta in southern Vietnam. The Nguyễn attempted to open friendship with Taksin. Taksin permitted Tôn Thất Xuân (Nguyễn Ánh’s uncle) and Mạc Thiên Tứ, the ruler of Hà Tiên, for the asylum in Thonburi after the Tây Sơn defeated them in 1778. However, the cordial relations were short, especially after the pirates robbed Thonburi junks near Hà Tiên. Taksin believed Cambodian officers who accused that Nguyễn Ánh sent spies to Thonburi. Taksin executed Tôn Thất Xuân, and Mạc Thiên Tứ committed suicide (Trịnh, 1972; Quốc Sử Quán Triều Nguyễn, 2007; Vũ, 2006). Not long after that, Taksin was dethroned and succeeded by King Rama I in 1782.

Figure 3 Shrine of Nguyễn Ánh on Phú Quốc Island, one of the routes used for seeking refuge in Siam.

Source: Photo by Sujane Kanparit (2013).

The second political asylum of the Nguyễn family in Siam involved Nguyễn Ánh, who maintained long-standing cordial relations with King Rama I. Before seeking refuge in Siam, Nguyễn Ánh tried to contacted Pierre Pigneau de Behaine in Chanthaburi for the assistance from France. After that, he used the sea route along the Gulf sailed from Hà Tiên, Phú Quốc, Ko Kut, Ko Si Chang to Paknam. On his way to Bangkok, a Vietnamese woman residing in Chanthaburi provided him with supplies and assistance (Trịnh, 1972; Quốc Sử Quán Triều Nguyễn, 2007; Vũ, 2006). Nguyễn Ánh lived in Bangkok for only a few years and came back to Vietnam using the same maritime route.

The sea route along the east coast of the Gulf served as a vital corridor for movement and refuge, underscoring the centrality of maritime connectivity in regional mobility. This case highlights not only the enduring importance of sea routes in facilitating political and social exchange but also the significance of women’s roles within the littoral communities of the Gulf of Siam. Economically influential local women frequently played active roles in assisting political exiles and heirs of ruling families during periods of upheaval. In port towns such as Chanthaburi, their involvement was evident through the provision of material support, mediation, and refuge—acts that sustained networks of loyalty and protection across shifting political frontiers. These dynamics, as will be further discussed in a later section, reveal how women’s agency was integral to the resilience and continuity of maritime societies in the Gulf.

Siamese-Vietnamese Tensions during the 1830s–1840s

The protracted war between Siam and Vietnam was last long until the reigns of Emperor Minh Mạng and King Rama III. From the 1830s to the 1840s, the sea space along the east of the Gulf became the area of power contestation again. The prolonged war between the two courts over Cambodia occurred both by land and sea. Hà Tiên and Chanthaburi were still a military base for naval forces. King Rama III sent troops led by Chaophraya Bodindecha to Hà Tiên and Châu Đốc in late 1833, which was not long after Siam agreed to help the Lê Văn Khôi rebellion to oppose Minh Mạng’s rule in Southern Vietnam. Lê Văn Khôi was the adopted son of Lê Văn Duyệt’s, one of the most powerful generals of the Nguyễn court. Siam wanted to reduce Vietnamese incursions into the Cambodian territory, which was under Siamese influence. However, the Vietnamese forces drove out the Siamese troops (Phumplab, 2010). In Chanthaburi, Siamese troops prepared for the Nguyễn troops. King Rama III assigned Chaophraya Phra Khlang to move the local people from Chanthaburi estuary to the Nern Vong hill because this hill was a better strategic point to see the Vietnamese forces over Chanthaburi estuary and Leam Sing cape. Chanthaburi, however, was not defeated by the Nguyễn troops. These naval wars were the last battle over the eastern coast of the Gulf (Thiphakorawong, 2012).

Both Siamese and Vietnamese rulers, therefore, projected the sea space on the east coast of the Gulf as the strategic point. They tried to compete and expand their political sphere of influence for more than half a century. Because both kingdoms and their oversea Chinese network knew the geographical location over the Gulf very well, they were not attacked by one another, except only once when King Taksin seized Hà Tiên in 1771. This development marked a significant transformation in the conception of power in mainland Southeast Asia. Whereas political authority had traditionally been anchored in inland capitals and territorial strongholds, the Thonburi period witnessed a decisive shift toward the maritime realm. From the reign of King Taksin onward, coastal towns and sea routes emerged as vital strategic bases that had to be secured and maintained as extensions of royal power. Consequently, the maritime sphere became integral to the projection of both Siamese and Vietnamese sphere of influence, transforming it from a peripheral zone into a central arena of statecraft, competition, and political legitimacy between the two kingdoms.

Trade prosperity and the ports along the east coast of gulf of Siam

Not only the political-strategic point, but the east coast of the Gulf was also a significant trade route for Siam and Vietnam. King Taksin, the Chakri dynasty, and the Nguyễn dynasty were a new dynasty that had just passed the internal and regional wars. As the new kingdom, Siam and Vietnam needed a high amount of money to strengthen the political power (Eoseewong, 1982). The most profitable way came from junk trade, particularly with China. During this period, either intentionally or unintentionally, Siamese and Vietnamese rulers became competitors in business.

Since the late seventeenth century, vast numbers of Teochew migrated to the east coast of the Gulf, i.e., Chanthaburi and Trat. These two towns subsequently became wealthy entrepot. Siamese regional trade on the east coast relied on Chinese settlements in Bangplasoi, Bangpra, Banglamung, Rayong, Chanthaburi, Thung Yao, Koh Kong, which functioned as vital pathways in the maritime trading network. This commercial sphere also extended into the littoral zones of Cambodia, where small coastal ports connected to inland markets through riverine routes. Cochin China and Cambodia were also the important trade partners of Siamese junks trade at Kampongsom, Hà Tiên, and Cà Mau, where were exchange places with Chinese, Indian and European goods (Viraphol, 1977). The overall pattern of regional trade between Siam and Vietnam was closely shaped by the shifting political relations between Bangkok and Huế, reflecting the deep interdependence between maritime commerce and interstate diplomacy in the Gulf of Siam.

In terms of maritime commerce, Hà Tiên and Chantaburi had developed to be the most important ports on the east coast of the Gulf. Hà Tiên was expanded as the entrêpot of the Gulf before Chanthaburi. Alexander Hamilton, who traveled to Siam and Cochin-China between 1689 and 1723, stated that “…Ponteamass, a place of pretty good trade for many years, having the convenience of a pretty deep but narrow river…that was suitable to trade with Cambodia” (Smithies, 1997). The location of Hà Tiên, which linked the hinterland in the western frontier of Vietnam and Cambodia, was the potential factor in making it a well-known trading entrepôt. (Sakurai & Kitagawa, 1999). Local products consisted of pepper, betel nuts, tin, blackwood, nutmegs, cloves, deerskins, dried shrimp, rattan, sappan wood.

Hamilton also mentioned about Chanthaburi as the territories of Siam and the place of “…for fifty leagues and more along the seashore, there are no seaports, the country being almost a desert.” (Smithies, 1997, p. 185). However, Chanthaburi had been developed to be the êntrepot after Teochew migrated and cultivated pepper in the late eighteenth century and exported to China (Reid, 2004). In 1821, it was remarkable as “one of the richest and the most valuable provinces of the king of Siam” (Finlayson, 1988, p. 255).

The geographical location of these ports was suitable for agricultural cultivation with extensive forests and fertile valleys and plains. Climate conditions also granted these ports for agriculture and increased trade (Warington, 1898). The main product of Chanthaburi, Kampot, and Hà Tiên was pepper. In Chanthaburi, a massive quantity of pepper was planted at the foothills and produced around 30-40,000 piculs or 4-5.2 million lbs. per annum (Viraphol, 1977; Finlayson, 1988; Mouhot, 1989). The potential cultivation also increased to an unlimited extent. Chanthaburi also exported benzoin, gambodge, cardamoms, lac, ivory, agila wood, tobacco, vast quantities of salted and dried fishes, dried leeches, tortoiseshells, rhinoceros’ horns, deer skins, hides of cows, buffaloes, and deers. It also produced gold in the east of the harbor and a popular place for precious stones such as Bangkacha island (Warington, 1898; Finlayson, 1988; Mouhot, 1989). Although Chanthaburi produced pepper and exported forest products, it could not transport other products from the other region for export. On the contrary, Hà Tiên was better at building a product network in the Mekong delta, especially started to export rice in the 1800s (Reid, 2004).

Chanthaburi and Hà Tiên had similar goods, especially pepper. Both towns were the maritime trade rivals. After the fall of Ayutthaya, besides the political reason, economic benefits were also a significant factor that brought different groups of Chinese competed with each other. When Cantonese expanded the power to the Gulf, it directly affected the benefit of the Teochew in Chanthaburi and Trat (White, 1972; Reid, 2004). The Siamese and local Vietnamese rulers used Teochew and Cantonese merchants in these regional ports to support their economic power. At the same time, the Chinese traders also gained benefits from the junks trade. Therefore, the sea space on the east coast was the strategic point of the economy for supporting Siam’s and Vietnam’s economic power.

Vessels sailing to these ports were mostly Chinese junks. The Nguyễn lords had shipbuilding technology before the eighteenth century. They had learned this technology from China and Champa. Between 1778 and 1819, the Nguyễn was able to build more than a thousand ships in various types. (Li, 2004) Undoubtedly, Vietnam had industrial shipbuilding using for trade and war.

Siam hired Chinese and Cham immigrants to build vessels and junks since the Ayutthaya period because the Siamese were not familiar with sea technology. The excavation team of underwater archaeologists has interestingly found traces of the shipbuilding industry in Chanthaburi, located along Chanthaburi river for six kilometers in two areas – the Laem Sing estuary and along the township area of Chanthaburi. They found many ship wreckages in the mangrove forest area. Most of the ship wreckages were the Fujian junk and the shipyard, possibly the wet docks for dragged ships from the river mouth to repair when high tide from the influence of the moon (Warington, 1898). However, a different assumption about the shipbuilding along the east coast raised by Li Tana argued that the potential of Chanthaburi for shipbuilding in the late eighteenth century was probably not enough for building many ships or junks in a short period. Shipbuilding technology in Chanthaburi was still in the beginning at that time (Li, 2004). However, the vessels found in Chanthaburi were probably built by the Chinese because the forests were abundant of excellent timbers, which were the best raw material for shipbuilding (Finlayson, 1988; Warington, 1898). Furthermore, the sites were possibly dockyards for repairing ships and junks.

Both the Chinese community of Chanthaburi and Hà Tiên strategically leveraged the expanding economic and geopolitical landscape to develop their ports into pivotal hubs of Chinese maritime trade and capital. In doing so, they became principal beneficiaries and intermediaries in the broader southward relocation of Chinese economic activity into maritime Southeast Asia.

Littoral communities along the east coast of the gulf of Siam

Seaports were inherently cosmopolitan with mixed races. The east coast of the Gulf was characterized by high mobility, attracting not only different Chinese ethnic groups but also Vietnamese, Malay, Cham, and Khmer (Reid, 2004). In the seventeenth century, the islands in Southern Vietnam had Makassars to serve as soldiers (Smithies, 1997). Hà Tiên troops were also diverse, consisting of Cantonese, Vietnamese, and Bugis. Chinese were the largest and most influential groups. In the 1820s, Crawfurd and Finlayson observed that the populations included Chinese, Cochin Chinese, Cambodians, and Siamese. Among them, the Chinese were all wealthy and profitable from commerce (Finlayson, 1988).

Seaports thus served as convergence points of multiple ethnic groups, who gathered to trade, reside temporarily, or settle permanently. These maritime communities retained links to their homelands yet remained only loosely integrated, and at times completely autonomous, from central political authorities (Hang, 2025). The diverse littoral societies along the Gulf, including Teochew merchants, Vietnamese Catholics, Cham sailors, and local Khmer communities, formed the social base of a hydrarchy. Their shared experience of mobility, exile, and economic interdependence produced forms of belonging detached from territorial states. In this sense, hydrarchy captures not only the economic but also the cultural and affective dimensions of maritime life, reflecting the solidarities born from navigation, risk, and displacement.

Along the Gulf’s coastline extending to southern Vietnam, Chinese communities displayed a greater degree of integration and hybridity than those in the traditional Chinese heartlands. This resulted from their constant interaction with multiethnic societies. In Hà Tiên, for example, the Mạc family cultivated close ties with Vietnamese commercial and administrative networks, adopting elements of Vietnamese language and dress. Such dual identities afforded them a distinctive status, elevating their position above both ordinary Chinese settlers and local Vietnamese elites (Hang, 2025). The Mạc polity itself reflected the coexistence of two overlapping political systems. While both the Sino-centric tributary system and the Southeast Asian mandala model valued loyalty and the recognition of superior power, the latter was far more flexible and informal, based largely on personal charisma and localized authority. Consequently, the Mạc family could simultaneously pledge tributary allegiance to Vietnam in accordance with the Chinese world order, while also sending tribute to the Cambodian and Siamese courts following regional Indianized Southeast Asian norms (Hang, 2025).

These port cities also relied on Malay and Austronesian maritime networks, which connected the Gulf of Siam to the Straits region and the Malay–Sumatran world, fostering close ties with Chinese merchant communities in Batavia (Hang, 2025). Scattered Austronesian-speaking communities were found along river mouths and coastal areas of the Gulf, some living permanently on boats. These seafaring groups were likely related to the Orang Laut, maritime peoples active around the Malacca Strait and Sumatra, who engaged in fishing, small-scale trade, and, at times, piracy along major shipping routes (Trinh, 1972). To strengthen their maritime defenses, the Mạc family formed a naval corps of Austronesian seafarers renowned for their mastery of the Gulf’s navigational networks and their wide-ranging connections throughout insular Southeast Asia. Their specialized skills were crucial in anti-piracy campaigns (Trinh, 1972).

The central coastal plain of the Gulf—stretching continuously from Siam through Cambodia to southern Vietnam—thus formed a vital connective zone. While most Khmer communities tended to settle inland on higher terrain, both Khmer and coastal peoples ventured out to fish among the Gulf’s many forested islands, which provided abundant marine resources (Taylor, 2014; Kitagawa, 2005).

In addition, the Vietnamese (Cochin Chinese) was also the high mobility group that moved between the east coast of the Gulf. No evidence found that the mass of the Siamese migrated to live in Vietnamese ports. Chanthaburi was the most explicit example to portray the settlement of the Vietnamese littoral community. The Thais call the Vietnamese as “Yuan.” Currently, Chanthaburi is the largest place for the Catholic community in Thailand. The community has around 10,000 people. Most of the followers are Vietnamese descendants from Cochin China. They have already assimilated into the local Thai society (Luang Sakhorn Khotchakhet, 2009). The local people identified themselves during the reign of King Rama VI as the Vietnamese descendants from their surname, which classified from the word “A-Nam” (means Annamese). Christianity is the common aspect that linked between Vietnamese groups rather than the recognition of the same ethnic identity.

The settlement of Vietnamese in Siam had emerged since the Ayutthaya period, as seen in the map of Ayutthaya drawn by Simon de la Loubère in 1691 that the Cochin Chinese community located near international communities (Goscha, 1999). Chanthaburi was the strategic point for the French missionary as it was a base when they escaped from the religious persecution in Ayutthaya and Cochin China. Catholic followers from Cochin China used this place as a resident as well as a shelter. After King Narai was dethroned, Ayutthaya changed the policy during the reign of King Phetracha. In 1688 the French priests and missionaries used Chantaburi as a shelter. In 1765, two years before the fall of Ayutthaya, the Vietnamese sought asylum by heading to Chanthaburi, where the Catholic community settled down earlier. (Launay, 1920)

French missionary sources recorded that 130 Cochin Chinese lived there worked as fishermen and petty merchants in 1710. French missionaries evangelized Christianity among them. When the missionaries began to rebuild their bases in Siam in the early eighteenth century, they focused on the Cochin Chinese who escaped the Ayutthaya repression by fleeing to Chantaboun. Besides the French priests, a multilingual Cochin Chinese priest named Vincent Len also played a vital role in this mission (Goscha, 1998). When Ayutthaya collapsed, some Catholic Cochin Chinese took refuge in Chanthaburi and along the coast of Cambodia (Kampot) to the south of Hà Tiên. Pineau de Béhaine, the French priest, also played an important role in evangelism from Chanthaburi to Cochin China. When the civil war broke up in Vietnam, he sent other Vietnamese emigrants to the east of the Gulf (Goscha, 1998). Nguyễn Ánh attempted to contact him and asked for assistance from France. In the 1820s, around three hundred Christians settled down there under the bishop of Metellopolis, the same as the other part of Siam (Finlayson, 1988; Terweil, 1984).

The Vietnamese immigrated to the east coast of the Gulf because of the political crisis, social dislocation, and trading reasons. In the 1780s, when Tây Sơn troops defeated Nguyễn Ánh, more than 300 mandarins and 1,000 followers sought asylum in Bangkok. They used the route from the east coast of the Gulf to Bangkok. Nguyễn Ánh started to build the regional and international alliance, i.e., French, Portuguese, English, and Chinese traders, by using the familiar route along the Gulf (Quốc Sử Quán Triều Nguyễn, 2007).

Since the eighteenth century, Vietnamese were a majority among the several thousands of populations in Chanthaburi, which was a similar portion to Chinese. More than five thousand Vietnamese lived in the fishing villages and made the pepper plantations, similar to Chinese (Warington, 1898). Vietnamese had been increasing their maritime activities with the regional ports from Rạch Giá in Mekong Delta to Chanthaburi. Vietnamese merchants sailed to trade in Bangkok and stopped by Koh Si Chang (Si Chang Island) and built a temple in 1826 (Goscha, 1998). They dominated the maritime trade along the islands from Phú Quốc to Koh Kong. They were the supplier of fresh fish and fruits from Bangkok along the shoreline (Goscha, 1999).

In the reign of Emperor Minh Mạng, during the Lê Văn Khôi rebellion in the 1830s, Chanthaburi and Trat were the locations for the political and religious asylum again. Emperor Ming Mạng’s policy on religious persecution led to the migration of Catholic Cochin Chinese to the eastern ports of the Gulf, i.e., Chanthaburi, Trat, Rayong, Chonburi, and Samut Songkhram (Poole, 1970). Half of the population in Chanthaburi were Vietnamese, which meant 3,000 Vietnamese out of 6,000 people were the total population (Goscha, 1999).

Siamese perceived Vietnamese as a professional in the marine activities. In the poem composed by Krom Khun Det-adison at Wat Pho during King Rama III period, it wrote that “… [The Vietnamese] are a race with many faces, and they have many tricks up their sleeves. They are skillful carpenters. They love to eat crocodile meat. They settled along the river and were experts about boats” (Krom Khun Det-adison, 2003, p. 42).

Furthermore, the Vietnamese littoral society in Chanthaburi was closely associated with Catholicism. They wore Vietnamese custom long blue dress and lived near the Roman Catholic church along Chantabun River. That area became the dock of Vietnamese communities. The Vietnamese were “industrious and thrifty, and among other occupations, they make an admirable class of colored mat” (Warington, 1898, p. 172). Vietnamese women were skillful for boat sailing. The Vietnamese worked hard, particularly women. They worked more than ten hours at a stretch in their heavy open boat by three women, which was not the given task for Siamese women (Warington, 1898).

The role of women was crucial in the expansion of maritime influence and in mediating commercial and political networks across the Gulf’s coastal societies. Many Chinese merchants established marriages with local women, including Vietnamese, Khmer, and Siamese, reinforcing cross-cultural and economic connections. Some women from wealthy or educated families also married Chinese merchants or court officials, and these women often wielded considerable influence in administrative and political decision-making. One notable instance involved the negotiation for the release of French missionaries from a local official’s custody (Phạm, 2013; Hang, 2025).

Women also played active roles in trade and the circulation of goods, and they frequently traveled aboard Chinese junks (Reid, 1993). As discussed earlier, the case of the local Vietnamese woman in Chanthaburi who aided Nguyễn Ánh further illustrates women’s agency in moments of political uncertainty. Moreover, the multiethnic character of these port societies created a degree of autonomy that enabled the Catholic Church to establish a robust institutional presence. The Church in these communities provided integrated programs of welfare, education, and spiritual instruction for men and women alike. Those demonstrating ability were trained alongside clergy, while others became healers or, among women, sisters (nuns) devoted to caring for the poor and the sick. These roles granted women a significant social and religious presence within the maritime world (Keith, 2012; Hang, 2025).

These cases highlight how maritime interconnection and gendered agency were deeply intertwined to the functioning of both the water frontier and the hydrarchical order shaping the Gulf. Within this dynamic maritime sphere, local women of economic and social standing acted as vital mediators, patrons, and protectors in times of political instability. Their roles in offering material support, refuge, and negotiation to elite families demonstrate that authority in the region extended beyond royal courts and merchant elites, being equally sustained through gendered and community-based networks along the coast. Their activities reveal that political authority in the maritime world operated through fluid, gendered, and relational forms of power, characteristic of a hydrarchy in which governance was negotiated through mobility and exchange across regional boundaries.

Conclusion

After the fall of Ayutthaya until the emergence of the French colony in Vietnam, the eastern coast of the Gulf of Siam had flourish interactions, politically and economically. Sea space was meaningful to both the Vietnamese and the Siamese during the regional interregnum. The sea route from Bangkok, Chonburi, Rayong, Chanthaburi, Kampot to Hà Tiên was crucial from different groups for various purposes. Naval warfares between King Taksin and the Nguyễn lords was represented by the Mạc family, as well as between King Rama III, and Emperor Minh Mạng subsequently.

The significance of the open sea and small ports along the eastern shoreline of the Gulf linked the regional ports together. This unit of sea space was the strategic political point for the Siamese and Vietnamese rulers. These small seaports were the vital points for the navy reinforcement. By interpreting this region through the framework of hydrarchy, the study reimagines the Gulf not as a passive route of state expansion but as a socio-political sea world in which power, mobility, and identity were constantly renegotiated among rulers, merchants, and littoral communities. These maritime societies sustained imperial economies while cultivating their own forms of autonomy and governance, illustrating how authority in the maritime realm was distributed rather than centralized. Mobility itself operated as a mechanism of power, blurring the boundaries between sphere of influence and seafaring agency.

The sea space on the eastern coast of the Gulf was the main route for the junk trade that sailed from the South China sea. The geographical characteristics along the coastal area that consisted of the inner bays in towns reduced the wind force and were suitable for the junks. Chinese migrants and Chinese traders were the significant groups that enlarged the political and economic power of the Siamese and Vietnamese new kingdoms in the period of the political interregnum. Chinese migrants, mainly Cantonese and Teochew, were able to collect abundant natural resources from the forests. These ports were suitable for mooring ships and junks, had enough freshwater, and safe from storms.

The relations between local rulers and Chinese who settled along the coastline between Siam to Cochinchina were reciprocal. Chinese littoral communities played a significant role in supporting the Siamese and Vietnamese rulers in terms of maritime trade, introducing shipbuilding technology as well as military assistance. The Siamese and Vietnamese also benefited to Chinese maritime commerce and used them as their intermediary for supporting economic power.

Thai and Vietnamese national histories rarely mention about how this unit of sea space and the small ports were essential for the state restorations. During the period of cordial relations between King Rama I and Emperor Gia Long, this sea space was used for mutual support between Siam and Vietnam, i.e., providing the supplies such as rice. However, this sea space was also the area for political and military contestation in the reign of King Rama III and Emperor Minh Mạng. Nowadays, Chanthaburi is perceived as a small province in the eastern part of Thailand. Similar to Hà Tiên, it is remembered as a little town on the Cambodia-Vietnam border. It is a problem of national historiography, which has primarily concentrated on land-based issues. Significantly, the eastern coast of the Gulf made enormous benefits for supporting the political and economic power of Siam and Vietnam. Furthermore, this coastal area was tremendous mobility of littoral communities that have connected for centuries.

Acknowledgments

I would like to express my sincere gratitude to The Empowering Network for International Thai and ASEAN Studies (ENITAS) Research Scholarship, Chulalongkorn University, Thailand, for the funding support in 2020 that enabled the development of this research project. I am also deeply thankful to Professor Dr. Leonard Andaya, whose invaluable inspiration and encouragement played a key role in shaping this topic in 2018 into a full research project. My heartfelt thanks also go to Sujane Kanparit and Vũ Đức Liêm for their generous assistance in providing annals and source materials. I would also like to extend my appreciation to the reviewers for their valuable comments, which have helped make this article more comprehensive and strengthened its arguments.

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