Cambodia to Assert Maritime Rights in Disputes

Thai security agencies say Cambodia’s formal move to adopt the 1982 United Nations Convention on the Law of the Sea (UNCLOS) is aimed at preserving and asserting its maritime rights amid disputes with Thailand and Vietnam. The decision reflects on Thailand’s proposed cancellation of a 2001 memorandum of understanding on overlapping continental shelf claims and is seen as a strategic legal response. Officials believe the move could shift future disputes towards international arbitration mechanisms.

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Cambodia ratified UNCLOS on March 6, 2026, despite having been a State Party since 1983, saying the move was intended to preserve and assert rights, thus prompting analysis from Thai security agencies. They identified two key drivers: Thailand’s decision to cancel the 2001 MOU44 agreement and revert to UNCLOS frameworks, and Vietnam’s infrastructure plans linked to the 2027 Asia-Pacific Economic Cooperation summit. Vietnam intends to build a road and bridge of more than 40 kilometres connecting its mainland to Phu Quoc island.

Phu Quoc lies in the Gulf of Thailand and has long been a point of contention, with Cambodia claiming rights over surrounding waters due to its proximity of around 24 miles from the Cambodian mainland. Vietnam maintains control of the island, which is about 35 miles from its own coast, supported by military and administrative presence. Thai analysts suggest Cambodia’s UNCLOS move strengthens its legal position in any future negotiations or disputes over maritime boundaries.

The situation is further complicated by Cambodia’s Funan Techo Canal project, scheduled for completion in 2028. The 180-kilometre canal will connect the Mekong River at Prek Takeo, south-east of Phnom Penh, to coastal areas including Kep, linking inland waterways with ports such as Sihanoukville and Kampot. Cambodian documents submitted to the Mekong River Commission outline a 100-metre-wide, 5.4-metre-deep channel, with infrastructure including three watergates, 11 bridges, and 208 kilometres of associated walkways.

Vietnam has raised objections to the canal, citing concerns it could alter currents at the Mekong River mouth, known as the Nine Dragons River. Analysts view Vietnam’s planned bridge to Phu Quoc as a countermeasure to Cambodia’s canal ambitions, reflecting growing regional competition over infrastructure and maritime access.

The Nation reported that Thai agencies expect tensions over maritime claims and infrastructure projects to continue, with legal frameworks such as UNCLOS likely to play a larger role. Future developments may involve international arbitration as countries seek to secure strategic and economic interests in the Gulf of Thailand.

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Adapted by ASEAN Now Nation 4 May 2026