Residents of Mae Sai demand end to cross-border mining pollution
On 23 September 2026, hundreds of farmers and villagers from Mae Sai district in Chiang Rai staged a quiet but determined protest, demanding immediate action against toxic sediment flowing into their rivers from illegal mining operations in Myanmar. The demonstration, organized under the slogan “Mae Sai (Stop Mining) — Toxic Mud Fills Homes, Toxic Substances Fill the Town,” brought together residents whose lives, livelihoods, and water sources have been steadily compromised over the past two years.
Arsenic levels in the Sai River exceed WHO safety limits by 28 times, according to data confirmed by Thailand’s Pollution Control Department. Lead, cadmium, nickel, mercury, and cyanide have also been detected in water samples taken along tributaries feeding into the Mekong. These contaminants, carried by seasonal floods and runoff from unregulated mines, now persist even in dry months — turning once-fertile riverbanks into zones of ecological and economic decline.
The source lies 25 kilometers inside Myanmar’s Shan State, near the town of Yon, where gold and rare earth mining has surged since 2022. Many of these sites operate under the control of ethnic armed groups and are linked to Chinese investment, making oversight nearly impossible. At least three mining clusters lie within 2.6 kilometers of the Kok River, a key tributary shared by both countries. The lack of containment measures — such as waste ponds or sediment barriers — means slurry and chemicals flow directly into waterways during rains.
Seven residents tested positive for arsenic accumulation in their bodies, and tap water in four villages across Chiang Rai province has shown contamination above safe thresholds. Mae Fah Luang University has documented neurological and musculoskeletal symptoms consistent with chronic heavy metal poisoning among those living along the riverbanks — symptoms that have worsened since the major flooding of 2024.
Farmers have seen their income vanish, even when crops test below official safety limits. Buyers refuse to purchase corn, roselle, and pumpkins grown near the Kok River, fearing market rejection. There is no compensation fund from the Ministry of Agriculture for losses tied to cross-border industrial pollution — only disaster aid for floods or droughts applies.
In response, the National Water Resources Committee has approved the construction of a new water treatment plant — the Mae Lao facility — to shift raw water supply away from the contaminated Kok River. Construction will begin in 2027 and finish in 2029, serving over 300,000 people in Chiang Rai, Wiang Chai, and Mae Lao districts.
Diplomatic efforts are stalled. Thailand and Myanmar established a Joint Working Group in 2025 to co-manage transboundary water quality, including joint sampling and pollution investigations. But Myanmar has removed clauses requiring shared evidence collection and on-site verification from the final draft. Thai officials now fear the agreement has been reduced to a symbolic information exchange — not a tool for accountability.
In protest, environmental activists have previously gathered at the Myanmar Consulate in Chiang Mai and the Chinese Embassy in Bangkok, calling for pressure on both governments. The Mae Sai community submitted eight specific demands to both nations: shut down upstream mines, hold public hearings, compensate affected farmers, manage toxic sediment, restore river health, ensure diplomatic pressure on Myanmar, install real-time water monitoring, and recognize the crisis as a national emergency.
While Thailand moves to alter its water infrastructure, the root cause remains out of its reach. For now, residents live with the silent, slow-moving crisis — drinking filtered water, abandoning fields, and watching their children grow up under an invisible threat that crosses borders but not responsibility.
