An increasing number of deformed fish have been found in the Kok, Sai, Ruak, and Mekong rivers in northern Thailand during May 2025, prompting environmental concerns and public health fears among communities in Chiang Rai province.
Fishermen operating along the Kok, Sai, Ruak, and Mekong rivers reported a surge in fish deformities last month, with many catches displaying visible lumps. The issue has raised alarm over potential contamination of the rivers and the impact on food safety.
According to the Living River Siam Association, a non-governmental group advocating for the protection of river ecosystems, the deformities may be linked to pollution from upstream gold mining operations in Shan State, Myanmar. These mines, reportedly run by Chinese investors in areas controlled by the United Wa State Army, are suspected of discharging untreated wastewater containing arsenic and heavy metals into local waterways.
The contamination is not only affecting aquatic life but also the livelihoods of local fishermen, who report growing difficulty selling their catch due to consumer concerns about toxicity. In response, samples of the deformed fish have been sent for laboratory testing to assess the levels of pollutants.
Somkiat Kuenchiangsa, president of the Living River Siam Association, stated that the matter extends beyond economic losses for fishermen, describing it as a broader environmental and food security issue with potential long-term effects on communities that depend on these rivers.
Calls for action have followed from within Thailand’s legislature. The Senate committee on natural resources and environment has urged the government to convene a meeting of the Mekong River Commission (MRC). The committee’s chair, Chivaparb Chivatham, has recommended that China and Myanmar—countries upstream on the Mekong and Kok rivers—be included in the commission’s framework. Currently, only Thailand, Vietnam, Laos, and Cambodia are members.
Chivatham has also proposed that the MRC treaty be amended to formally include these upstream nations, arguing that their participation is necessary to resolve the transboundary pollution stemming from mining activities.
