Cambodia turns to UNCLOS conciliation after Thailand scraps maritime boundary pact

Gulf of Thailand: flashpoint in Thailand–Cambodia conflict. (Alexey Komarov)

On June 3, Cambodia formally decided to invoke “compulsory conciliation”, an international arbitration mechanism within the United Nations Convention on the Law of the Sea (UNCLOS), to resolve the Overlapping Claims Area (OCA) in the Gulf of Thailand.

“This is not an escalation of tensions. It is a facilitated negotiation between the two countries, supervised by international expert conciliators,” Cambodian Prime Minister Hun Manet said. He reiterated that Thailand’s unilateral move to revoke the 2001 Memorandum of Understanding (MoU 2001)—a bilateral framework for resolving overlapping maritime claims between the two countries for the past 25 years—prompted Phnom Penh to resort to the international treaty mechanism.

Prime Minister Hun Manet further assessed that the “compulsory reconciliation process” is aimed to protect Phnom Penh’s sovereignty and rights in the maritime border area, pledging to leverage diplomatic channels and international legal measures to end the border conflict and restore peace.

He said that his administration opted for a conciliation mechanism under UNCLOS as both Cambodia and Thailand are parties. Under the UNCLOS mechanism, the conflicting parties present their positions before a panel composed of five international law experts, who guide conciliation efforts.

Thai Prime Minister Anutin Charnvirakul, however, defended the cancellation of the 2001 maritime agreement, MoU 44, arguing that it had stalled compared to the 2000 land border agreement, MoU 43, which had achieved 60%t progress.

Thailand argued that Cambodia’s decision to use the international dispute mechanism also meant abandoning bilateral negotiations and ASEAN-led efforts, such as those discussed at the 48^th ASEAN Cebu Summit.

Thai Deputy Prime Minister and Minister of Foreign Affairs, Sihasak Phuangketkeo, underlined that the conciliation’s decision is not legally binding and prioritised bilateral negotiations, reiterating its preference to utilise the bilateral negotiation mechanism, such as the General Border Committee (GBC) and Joint Boundary Commission (JBC).

The longstanding conflict between Cambodia and Thailand reflects a fragile truce agreement. While both governments publicly stress their commitment to realising peace, fresh military incidents involving security forces along the border lines highlight how stalled and politicised the issue has become.

Cambodia’s step to use the mechanism under UNCLOS signals a willingness to internationalise the conflict resolution. This new episode illustrates the broader challenge of managing territorial disputes in Southeast Asia to safeguard sovereignty, uphold regional diplomacy and resort to international law, all while preventing prolonged tension from turning into wider friction.