Kok River contamination

Communities along northern Thailand’s Kok River say water they once used for fishing, farming and tourism is now carrying toxic runoff from mines across the border in Myanmar. (straitstimes.com) The Kok rises in Myanmar’s Shan State, crosses into Chiang Mai province, then flows through Chiang Rai before joining the Mekong River. Thai officials began warning residents in March 2025 after tests found arsenic in the river above the 0.01 milligram-per-litre standard for natural water sources. (khaosodenglish.com; bangkoklocal.info) Rare earths are a group of minerals used in magnets for electric vehicles, wind turbines and electronics, and one common extraction method uses chemicals that can wash into streams if waste is not contained. The Stimson Center said unregulated mining in Myanmar’s Mekong Basin has sent toxic runoff into rivers that flow into Thailand and then the Mekong mainstream. (stimson.org) Researchers and Thai officials have tied the latest contamination fears to a mining boom that accelerated after Myanmar’s 2021 military coup weakened oversight in border areas. The Straits Times reported that Thai researchers found arsenic accumulation in residents living along the Kok River, adding a public-health concern to the loss of income. (straitstimes.com; stimson.org) The problem is no longer only local to the riverbank. The Mekong River Commission said arsenic contamination was first identified in March 2025 near the Kok and Ruak confluences in northern Thailand, and that monitoring later showed fluctuating levels in the upper Mekong. (mrcmekong.org) Thai agencies have responded with repeated sampling and emergency spending. Thailand’s Pollution Control Department has tested water twice a month and sediment monthly since March 2025, and the cabinet later approved more than 188 million baht for pollution response projects in Chiang Rai. (en.thairath.co.th; chiangraitimes.com) Local residents say the damage shows up in everyday decisions: whether to cast nets, irrigate fields or take tourists onto the water. Stimson Center researchers reported that people along affected rivers have stopped using them for fishing, that farm products are shunned in Thai markets, and that families fear long-term exposure to toxins. (stimson.org) The mining itself is part of a larger supply chain that reaches far beyond the Thai-Myanmar border. New satellite analysis cited by the Business and Human Rights Resource Centre said more than 500 rare-earth mining sites were operating across Myanmar’s northern river basins in late 2025, including dozens newly opened that year. (business-humanrights.org) Reporting on the mines points to Chinese-backed operators and militias controlling parts of the border economy, but the pollution is borne downstream in Thai villages that did not profit from the boom. Thailand has pushed for talks with Myanmar and China as contamination in the Kok turned from a river-quality issue into a cross-border diplomatic dispute. (thediplomat.com; khaosodenglish.com) A year after the first Thai warnings, the Kok River has become a test of whether governments can police a minerals rush that feeds global clean-energy supply chains while fouling the water of people living downstream. (straitstimes.com; mrcmekong.org)