CHIANG RAI–On 8 May, Mr. Rangsiman Rome, chair of the State Security, Border Affairs and National Reform committee, chaired a meeting in Chiang Rai to address arsenic contamination in the Kok and Sai rivers.
The discussion included Chiang Rai governor Charin Thongsuk, officials, academics, and civil society groups. The rivers, which flow from the Wa-controlled area in Myanmar, have been found to carry dangerous levels of pollutants into the Chiang Rai rivers.
The meeting took place at the Chiang Rai City Hall. The Kok River enters Thailand at Mae Ai district in Chiang Mai province and flows through Chiang Rai city, while the Sai River forms the border between Thailand and Myanmar.
The Office of Environmental and Pollution Control, Region 1, reported repeated detections of arsenic above safe levels (more than 0.01mg/litre) in both water and sediment samples. However, water tested in the Mae Fang tributary showed good quality, pointing to an upstream source of the pollution. Now, officials collect and test water samples twice a month.
The Chiang Rai waterworks department uses around 48,000 cubic metres of water per day from the Kok River, supplying over 41,300 people. The Mae Sai waterworks supplies 9,300 cubic metres daily to about 9,500 people, and the Ruak River provides 7,200 cubic metres daily for 5,850 users. The water is treated with chemicals to remove heavy metals and keep turbidity below safe limits, making it safe to drink.
Chiang Rai fisheries also collected fish samples—including both plant-eaters and predators—along the river to test for contamination. Some fish, like the catfish with red bumps on gills and fins, were sent for lab analysis, with results pending.
Academics from Rajamangala University of Technology Lanna suggested the source lies 8.6km and 44.9km inside Myanmar. This pollution increases arsenic levels by 15-28%, with worse contamination during the dry season.
They recommended building a water barrier in Mae Ai to trap sediment before it flows downstream.
Dr. Suebsakul Kitchanukorn from Mae Fah Luang University explained that manganese mining near the Thai border used to release wastewater straight into the Mekong River, with minerals then imported to Thailand through Mae Sai customs.
Many investors, both Thai and foreign, are involved. He urged the committee to review which groups fund the gold mines at the Kok and Sai river sources and whether any produce is exported to Thailand, so solutions can be found.
Former senator Tuenjai Deetes believes local officials have done their best, but the root of the problem lies outside Thailand. She called on the government to push for solutions, even though Thailand is not the source.
Pienporn Deetes, secretary-general of the Community Development and Mountain Area Foundation, said arsenic contamination in the Kok River is a new problem. She stressed the need to act quickly, warning of worse impacts if ignored for years.
Rangsiman Rome and his team, including Manop Kheeripuwadol (vice chair) and Yuthipong Pipoppinyoyo (secretary), announced plans to set up a working group to coordinate with provincial authorities.
They will report their findings to the government and related agencies. They also asked the Internal Security Operations Command and local Thai-Myanmar border committees to check which groups or companies have mining concessions in the Wa area. The National Intelligence Agency might be asked to help gather information for talks with Myanmar and other countries.
Yuthipong said Chinese investors are unfamiliar with the area, so they often work with influential local groups. He asked security agencies to investigate and suggested using strong measures like cutting off power and fuel supplies, as done against call centre scams.
The military will raise the issue at the upcoming Thai-Myanmar Regional Border Committee (RBC) meeting, chaired by the Third Army Region Commander, with Myanmar’s RBC. The meeting, set for 2-4 July 2025, will include the river contamination as a main agenda item to inform Myanmar authorities.
