The Gulf of Thailand forms the second axis of the Cambodia-Thai border dispute. The 27,000-square-kilometer Overlapping Claims Area has been disputed since 1972 and is estimated to hold some 1.6 billion barrels of oil and 17 trillion cubic feet of natural gas. Thailand terminated the 2001 memorandum of understanding governing talks over the OCA in early 2026, after fighting along the two nations’ disputed land border in July and December 2025. The outbreak of war reignited historic territorial and political animosities between the two Southeast Asian states and resulted in a border closure that still persists.

The immediate cause of the fighting was a calculated political leak by Cambodian Senate President Hun Sen of a private 17-minute telephone conversation with Thai Prime Minister Paetongtarn Shinawatra. The recording exposed Paetongtarn adopting a deferential posture toward Phnom Penh while offering critical remarks regarding her own military commanders.

As Hun Sen no doubt intended, the political fallout in Bangkok was swift. The leak locked Thai political elites into a severe audience cost escalation trap, where public outrage severely restricted their diplomatic flexibility. Paetongtarn’s political credibility evaporated almost overnight, and a wave of hyper-nationalism culminated in her suspension and removal from office by the Constitutional Court. Domestic political discourse in Thailand became thoroughly militarized, effectively ending any immediate possibility of bilateral compromise with Cambodia.

Riding this surge of populist anger, Anutin Charnvirakul and his Bhumjaithai Party secured victory in the February 2026 election. Anutin formed a hardline government that explicitly prioritized security, deferring border management directly to military commanders. Fulfilling a key electoral pledge to his nationalist base, Anutin’s cabinet formally approved the unilateral termination of the 2001 MoU. For nearly 25 years, the agreement had provided the only framework for maritime boundary delimitation and joint energy development between the two neighbors.

To justify scrapping the agreement without a formal exit clause, Thai legal strategists invoked Article 56 of the 1969 Vienna Convention on the Law of Treaties, claiming an implicit right of denunciation based on Cambodia’s alleged failure to engage in negotiations. But the move was motivated above all by domestic politics: it was intended to project strength and to signal to voters that the legacy of former Prime Minister Thaksin Shinawatra, under whose administration the 2001 MoU was originally drafted, was officially over. However, by dismantling the agreement, Bangkok simultaneously destroyed the remaining institutional safeguards governing the maritime boundary.

Phnom Penh responded immediately to Thailand’s unilateral exit. Condemning the move as a breach of international legal obligations, the Cambodian government announced it would initiate compulsory conciliation under Annex V of the United Nations Convention on the Law of the Sea (UNCLOS). It was a shrewd political move. Having suffered a military defeat on the land border and remaining in an inferior position to its Thai counterpart, Cambodia was also facing increasing pressure from powerful states due to its domiciling the online scamming industry. Hun Manet engaged in forum shopping, choosing a legal avenue that promised low cost and high potential reward. By choosing compulsory conciliation, Cambodia has demonstrated its resolve to be a “good member” of the international community, pull Thailand into a non-binding, low-sovereignty-cost legal mechanism, and demonstrate to the Cambodian people a willingness to “stand up” to a superior opponent.

While compulsory conciliation might initially appear to exacerbate tensions, international legal design suggests that it could provide a necessary off-ramp for both countries. Under Annex V, proceedings are transferred to an independent five-member Conciliation Commission. As international relations theory emphasizes, third-party delegation fundamentally alters political dynamics by depoliticizing interstate friction. By placing complex maritime claims in the hands of neutral legal and hydrographic experts, the framework insulates negotiators from the volatile domestic audience costs that previously constrained leadership in both Bangkok and Phnom Penh.

Crucially, Annex V compulsory conciliation produces recommendations that are non-binding. This flexible design lowers sovereignty costs for both state parties, reassuring their leaders that participation does not entail an irreversible loss of national jurisdiction or offshore resources. In other words, the framework functions as an essential political circuit breaker. It introduces mandatory procedural time delays that allow hot-headed nationalist fervor to cool, while offering political elites a neutral, international body upon which to shift blame for necessary diplomatic compromises.

Pathways Forward through Conciliation

The practical viability of this mechanism was demonstrated in the landmark Timor-Leste v. Australia conciliation in 2016. In that case, Annex V conciliation successfully bypassed entrenched jurisdictional exclusions and deep bilateral hostility over the Greater Sunrise gas field. The independent commission used flexible mediation to guide both states toward a permanent maritime boundary while establishing a specialized joint development regime for energy extraction.

By issuing authoritative, independent technical evaluations, an Annex V Conciliation Commission provides state leaders with vital legal cover to resolve baseline incompatibilities, such as redrawing Cambodia’s baseline away from Koh Kood while establishing a median line that recognizes Thailand’s sovereignty over the island under UNCLOS Article 121 Because the recommended concessions originate from a neutral international panel, political elites can frame modifications as compliance with international law rather than domestic capitulation. Furthermore, conducting confidential proceedings in the Permanent Court of Arbitration (PCA) in The Hague coupled with a 12-to-18-month cooling-off period provides essential procedural insulation. This shields negotiators from volatile digital news cycles and interrupts short-term electoral mobilization, allowing executive leaders to escape the audience cost trap.

Beyond legal insulation, conciliation operationalizes “sequence inversion” by temporarily setting aside intractable boundary disputes to prioritize functional economic agreements. Under UNCLOS Articles 74(3) and 83(3), the Commission has the authority to establish interim provisional arrangements for joint revenue-sharing in the OCA. Engaging independent technical experts to model resource distribution reframes the dispute from a zero-sum territorial contest into a positive-sum economic distribution exercise.

It would be naïve to think UNCLOS conciliation is a panacea for the thoroughly ruptured relations between Bangkok and Phnom Penh. However, by Cambodia taking Thailand to international arbitration under an international regime designed for compromise with consensus and input from all parties, perhaps the prospects for peace can be reinvigorated. Given that The Hague has been jointly agreed as the PCA venue, if a reasonable proposal can be agreed to kickstart negotiations, Thailand may finally be able to exorcize the “ghost” of the “loss” of Preah Vihear temple to Cambodia in 1962.