Residents of Mae Sai district in Chiang Rai have formally petitioned the Thai government to intervene in a mounting environmental crisis, as toxic arsenic contamination from cross-border mining operations continues to poison the Mae Sai River.
Two years of intermittent pollution have left local communities—particularly in the Sai Lom Joy and Tham Pha Chom areas—without reliable access to clean water, according to reports from Thai PBS News.
The petition, submitted on November 11, 2026, to the Mae Sai district chief, demands that the Prime Minister visit the site to witness the extent of the damage firsthand.
The contamination has forced the Provincial Waterworks Authority in Mae Sai to periodically halt production, disrupting service for over 23,000 households, Manager Online reported. While the Ministry of Public Health has urged citizens to remain calm, officials confirmed that arsenic levels in raw water sources have consistently exceeded safety standards.
The agricultural sector faces a parallel threat. The Royal Irrigation Department has detected arsenic concentrations above safety limits in 11 soil samples and 23 rice crop samples irrigated by the affected river systems. Farmers are now grappling with the reality that their primary water source for over 110,000 rai of farmland may be compromising the safety of their harvest, a concern echoed by local agricultural groups.
According to research cited by Manager Online, there are at least 20 companies operating mines in the Tachileik area alone, including gold, manganese, and antimony operations.
The Ministry of Public Health, through the Department of Health, has issued clear guidance to mitigate long-term health risks. Officials have advised against drinking or using river water for cooking, washing vegetables, or irrigating crops until further notice.
“Boiling or chlorinating the water will not remove arsenic,” the Department of Health cautioned, as noted by RYT9. The government has spent at least 2 billion baht attempting to secure alternative raw water sources for the 40,000 households served by the Kok River system, yet the structural nature of the contamination remains unaddressed.
For now, the community continues to rely on emergency water supplies while the root cause of the toxicity, the upstream mines, continues to operate largely unchecked.
