Cross-border pollution from Myanmar’s gold mining and deforestation impacted Thailand’s Kok and Sai rivers, exacerbating flooding and contaminating water with toxic chemicals including cyanide, arsenic, and mercury. These activities, reportedly intensified since 2023 by four Chinese companies, led to ecological devastation, decimating fish populations and threatening the health and livelihoods of 1.2 million people. The September 2024 floods submerged villages including Peng Kham in Myanmar and Thaton in Chiang Mai with mud-laden water.

In response, over 700 Thaton residents rallied on March 14, 2025, for the International Day of Action for Rivers, demanding protection of the Kok River. Tests in Mae Ai district revealed alarming arsenic levels (0.026 mg/L, exceeding the 0.01 mg/L safe limit) and mercury (0.076 mg/L, above 0.05 mg/L), linked to cancer and neurological damage. Academics and civil groups petitioned Prime Minister Paetongtarn Shinawatra to negotiate with Myanmar’s junta, ethnic forces, and China, proposing a joint panel and water-quality monitoring centre.