The decades-old dispute of the Thai-Cambodia border that erupted on July 24, displacing 172,000 people within both countries internally[1] is still on-going, with no resolution in sight. The Prasat Ta Muen Thom, a Khmer-era Hindu temple, now rejoins the list of five others along with Chong Bok, Ta Krabey, Ban Hat Lek-Cham Yeam and the Prasat Preah Vihear. Despite several international dispute resolution mechanisms and regional institutional frameworks, Thailand and Cambodia’s difference on the means of resolving the dispute reflects their respective political ambitions. For Thailand, it advances the cause of reunifying former Thai territories to its modern state, potentially adding heritage sites to its tourist destinations. For Cambodia, it is crucial for retaining its sovereign territorial rights on heritage sites and preserving public trust.
The present territorial conflict with Cambodia dates back to 1954, when Thailand took control of Cambodian territories based on the Franco-Siamese treaty of 1904. This was one of the several Franco-Siamese treaties to resolve the 1893 crisis between the Siamese (Thai) kingdom and French colony in Indochina encompassing present-day Laos, Cambodia, and Vietnam.
The contestation is the outcome of significant territorial concessions made by Siam to neighbouring European colonial powers in the 1890-1900s. To preserve its independence, it ceded Battambang, Siem Reap, and Sisophon provinces to the French colony in the east, while transferring Kedah, Perlis, Kelantan, and Terengganu to the British colony in the south. These historical territorial adjustments have established the foundation for two of modern Thailand’s most persistent border challenges: territorial disputes with Laos and Cambodia along its eastern frontier, and ongoing separatist tensions along its southern border with Malaysia.
In 1962, the matter of contestation over Prasat Preah Vihear was brought to the International Court of Justice (ICJ) by Cambodia. The ICJ awarded territorial rights of the temple to Cambodia[2] based on Thailand’s longstanding ‘recognition and acquiescence’ of maps that followed the 1904 treaty and subsequent Siam-French Mixed Commissions for border settlement. In international law, ‘recognition and acquiescence’ refer to the unilateral discretionary act or implied consent to a situation of claim through diplomatic recognition. The state’s silence or lack of protest on border settlements is reflected as its tacit consent and interpreted as acceptance.
In stark contrast to its verdict, the ICJ additionally acknowledged that the border demarcated by the commissions failed to fully comply with the territorial settlements as per the 1904 treaty. This is what bears full responsibility for the festering of the border issues.
For nearly two decades, tensions have resurfaced periodically on the Thai-Cambodia border, exacerbated by domestic leadership challenges and nationalism. This included street demonstrations in Bangkok in 2008 in response to Cambodia seeking UNESCO World Heritage status for Preah Vihear, with border skirmishes following from 2008 to 2011. In 2013, Cambodia requested the ICJ to interpret the 1962 judgement,[3] this time securing the territory surrounding the Preah Vihear to Cambodia,[4] as a concrete step towards preventing future conflicts.
The present conflict has since evolved beyond a bilateral territorial dispute; it underscores the limitations of existing international legal frameworks and institutions in resolving complex historical boundary questions, particularly those involving cultural and religious heritage sites.
Southeast Asia’s latent territorial contestation requires a political resolution through a regional mechanism, whilst observing international norms. Cambodia holds the ICJ ruling at the core of its argument, and backs the July 2025 U.S-initiated ceasefire mediated by the Association of Southeast Asian Nations (ASEAN) as the way forward. Thailand rejects the ICJ award and ASEAN mediation, insisting on resolving it bilaterally. Therefore, a major hurdle in resolving the border issue is modern Thailand’s political will to rectify its own historical concessions.
The border tension serves as a critical test for ASEAN’s regional dispute resolution. Malaysia has iterated ASEAN centrality, mediating the conflict to contain potential spillover effects on other regional cross-border disputes.[5] However, it has failed in forging a durable consensus among the conflicting parties, thereby weakening ASEAN’s conflict resolution mechanism. A successful resolution could have established a precedent for managing similar regional and global conflicts on heritage sites, and elevated Malaysia’s role as a power-wielding member in Asia. The burden has now been shifted to the Philippines as new chair.
The inability to move beyond short-term stabilisation to resolution underscores the ongoing challenges facing the ASEAN, including its capacity, and the individual political will of member states over the collective. It raises questions about the organisation’s ability to address contentious bilateral conflicts that threaten regional stability and cohesion.
Unless resolved, the present conflict will keep evolving beyond flashpoints of nationalist sentiments and bilateral territorial disputes. Political use of history will continue to override treaty mechanisms, underscoring the shortcomings of existing international legal frameworks and regional institutions in resolving complex historical boundary questions, particularly in implementation and enforceability of norms in situations involving cultural and religious heritage sites.
Dipannita Maria Bagh is a Senior Researcher, Southeast Asia Studies Programme.
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References:
[1] World Health Organization, “Cambodia: Conflict on Thai border: Public Health Situation Analysis,” August 19, 2025, https://cdn.who.int/media/docs/default-source/2021-dha-docs/phsa-cambodia-190825.pdf
[2] International Court of Justice, Temple of Preah Vihear (Cambodia v. Thailand), 1962, https://www.icj-cij.org/case/45
[3] International Court of Justice, “Request for Interpretation of the Judgment of 15 June 1962 in the Case concerning the Temple of Preah Vihear (Cambodia v. Thailand),” 2011, https://www.icj-cij.org/case/151
[4] United Nations, “UN court rules for Cambodia in Preah Vihear temple dispute with Thailand,” November 11, 2013, https://news.un.org/en/story/2013/11/455062#
[5] Association of Southeast Asian Nations, “ASEAN Foreign Ministers’ Statement on Thailand-Cambodia Border Dispute,” July 28, 2025, https://asean.org/asean-foreign-ministers-statement-on-thailand-cambodia-border-dispute/