Cambodia has filed a complaint with the Organisation for the Prohibition of Chemical Weapons (OPCW), alleging that the Thai military used chemical weapons and other chemical substances during last year’s border conflict, according to Cambodian media. Thailand has denied the allegations.
The complaint was filed on September 11 following findings by the Cambodian Mine Action Centre (CMAC), which said 395 Cambodian civilians and security personnel had been affected by the alleged substances, the Phnom Penh Post reported.
CMAC Director-General Heng Ratana said the substances were allegedly delivered by aircraft and drones as well as through 155mm and 120mm artillery shells. He said evidence had been identified in civilian areas, including villages, farmland and a market.
“Chemical weapons and chemical substances were used. From a technical perspective, these are two different terms,” Ratana said.
CMAC also cited an analysis of 61 chemical samples collected in August 2025. According to the centre, one finding was classified as a chemical weapon under the Chemical Weapons Convention, while 22 others were identified as toxic or hazardous chemicals that are not prohibited by the treaty.
However, the complete laboratory report and details of the sampling methodology were not presented during the briefing.
Thailand has repeatedly rejected Cambodia’s allegations. In July 2025, the Thai Foreign Ministry described claims that its forces had used chemical weapons as “groundless” and part of a campaign of disinformation.
The Royal Thai Army subsequently rejected allegations concerning the use of white phosphorus munitions, arguing that such munitions are not classified as chemical weapons under the Chemical Weapons Convention.
The OPCW has yet to publicly determine whether prohibited chemical weapons were used in the conflict.