Thailand faces one of its biggest environmental disasters in decades as arsenic from gold and rare earth mines in Myanmar contaminates the Kok, Mekong, Salween and Kraburi rivers. A People’s Party MP says ministers failed to act despite UN warnings as pollution threatens health, farming, fisheries and tourism.
Thailand is confronting one of its worst cross-border environmental crises in decades as arsenic contamination linked to expanding gold and rare earth mining in Myanmar spreads from the Kok River into the Mekong, Salween and Kraburi river systems, threatening public health, farming, fisheries and tourism. With evidence increasingly pointing to mines in Wa-controlled territory and other armed enclaves in Shan State, a People’s Party MP has accused the government of staying silent despite mounting pollution, stalled diplomacy and growing United Nations concern.
A People’s Party MP has accused the government of failing to confront one of Thailand’s most serious cross-border environmental crises in decades after arsenic contamination linked to mining in neighbouring Myanmar spread beyond the Kok River into several major waterways.
The criticism came as evidence continued mounting that heavy metal pollution is threatening agriculture, fisheries, tourism and public health across northern Thailand. Yet, diplomatic efforts aimed at tackling the source of the contamination remain largely stalled.
Mr Phatarapong Leelaphat, MP for Chiang Mai, made the allegations in a Facebook post on June 24. He said the government was “not speaking, not acting and not addressing the root cause” of the crisis.
Government accused of ignoring expanding arsenic pollution as contamination flows into rivers
Instead, he argued that ministers had chosen to remain cautious towards neighbouring countries where the mining activity is taking place. As a result, Thai communities continue bearing the environmental cost of pollution generated outside the kingdom.
According to Mr Phatarapong, the problem has moved well beyond the Kok and Sai rivers, where contamination first attracted national attention. He said arsenic pollution is now affecting several major river systems entering Thailand. Therefore, he argued, the issue should no longer be viewed as an isolated environmental problem. Rather, it has become a national challenge involving public health, food security and international diplomacy.
“This is not just about rivers,” he wrote. “These are agricultural areas and water sources used by the public.” He added that heavy metals have already exceeded accepted safety standards in several locations. Consequently, he warned that livelihoods and public health are increasingly under threat.
The Chiang Mai MP said contamination in the Kok and Sai rivers has been reported for a prolonged period. However, he argued that public discussion has overlooked the broader picture. According to Mr Phatarapong, sediment in the northern Mekong River contains arsenic concentrations exceeding accepted safety limits by more than 30 times.
In parallel, fish collected from the Mekong in Loei province have reportedly been found with arsenic and lead above accepted safety standards.
Evidence shows arsenic contamination has spread from northern rivers into wider waterways across Thailand
Separately, he said the Salween River in Mae Hong Son has recorded arsenic concentrations reaching around five times Thailand’s accepted limit. On another front, he said the Kraburi River in Ranong province has registered turbidity levels considered severely hazardous to aquatic life. Taken together, he argued, the findings show heavy metal contamination spreading across several international waterways flowing into Thailand.
Mr Phatarapong said he has repeatedly raised the issue during parliamentary debates. Even so, he accused the government of remaining silent while contamination continued spreading through northern river systems. “This problem has existed for a long time,” he wrote. “Everyone can clearly see it.” Nevertheless, he said the government continues choosing “not to talk, not to act and completely ignores the issue.”
The MP argued that monitoring rivers after pollution reaches Thailand cannot solve the problem. Instead, he said authorities must confront the source of the contamination upstream.
According to Mr Phatarapong, many mining operations are located inside Myanmar in areas beyond the effective control of the country’s central government. Moreover, he said the number of mines continues to increase every year.
He also stressed that Myanmar is not the only country involved. Laos has also experienced extensive mining expansion. Meanwhile, trade data shows minerals moving from Myanmar through Thailand before continuing to China. In his view, that makes the contamination part of a wider regional supply chain rather than a purely bilateral dispute.
MP says Myanmar, Laos and China must be included in talks to tackle pollution at its source together
Despite those developments, Mr Phatarapong said Thailand has made little diplomatic progress. According to him, only one meeting has taken place with Myanmar. Since then, no meaningful follow-up has occurred. Beyond that, he argued the government has not attempted broader negotiations involving every country participating in the regional mineral trade.
The MP also criticised the government’s internal response. As chairman of the parliamentary subcommittee on transboundary water pollution, he said he has monitored the issue closely for years. He said a recent follow-up meeting involving the Ministry of Natural Resources and Environment and the Ministry of Foreign Affairs revealed virtually no progress.
Notably, officials presented neither an international negotiation strategy nor preparations by the working group chaired by Deputy Prime Minister Thongsak.
Mr Phatarapong also claimed the government’s international negotiating team has never met. Likewise, the official follow-up working group last convened in April. In response, he questioned how Thailand could eliminate pollution at its source while key government mechanisms remained inactive.
UN concern grows as MP says Thailand’s response remains stalled despite repeated international warnings
The MP also pointed to growing international concern. On April 21, the United Nations Human Rights Working Group sent urgent communications to the governments of Thailand, Myanmar and China. The letters also went to companies connected to mining activities. Even after those interventions, according to Mr Phatarapong, there has been no visible change.
“I urge the government to be courageous, speak out and act,” he wrote. He called for direct multilateral negotiations involving Thailand, Myanmar, China and Laos. According to the MP, Thai communities receive no benefit from many of the mines. Instead, they continue carrying the environmental burden created upstream.
His criticism comes as evidence increasingly links northern Thailand’s contamination to expanding mining operations across Myanmar’s eastern Shan State. The Kok River remains the most visible example. However, environmental researchers believe it represents only one part of a much broader cross-border pollution network.
The Kok River rises in Myanmar before flowing about 170 kilometres through Shan State. It then enters Thailand at Mae Ai district in Chiang Mai before crossing Chiang Rai and joining the Mekong River. Consequently, pollution released upstream crosses directly into Thai territory. Unlike domestic pollution, Thailand has little authority over activities taking place beyond its borders.
Rivers flowing from Myanmar carry contamination directly into Thailand before reaching the Mekong basin
Repeated testing during 2025 and continuing throughout 2026 detected arsenic concentrations above Thailand’s accepted safety standards at several locations along the river.
In addition, lead and other heavy metals have also been identified in multiple samples. Those findings have steadily strengthened concern among researchers, environmental agencies and local communities.
Investigators increasingly believe the contamination originates from expanding gold and rare earth mining operations inside Myanmar. Gold mining presents particular environmental risks because excavation exposes naturally occurring arsenic-bearing rock. Once disturbed, arsenic can enter surrounding soil and streams. Afterwards, seasonal rainfall carries contaminated sediment into tributaries feeding the Kok River.
Rare earth mining creates additional risks. Wastewater generated during mineral extraction may contain heavy metals if environmental controls are inadequate. Similarly, poorly managed tailings can release contaminated sediment into nearby waterways. For that reason, researchers believe both industries are contributing to the growing pollution flowing towards Thailand.
Gold and rare earth mining in Shan State is increasingly linked to arsenic contamination entering Thai rivers
Satellite imagery has identified dozens of mining sites close to tributaries feeding the Kok River basin. Many operate inside the Wa Self-Administered Division in eastern Shan State. The autonomous region is controlled by the United Wa State Army, or UWSA, Myanmar’s largest and best-equipped ethnic armed organisation.
Although the UWSA maintains a ceasefire with Myanmar’s military authorities, it administers much of the region independently. It controls local security, administration and governance. Consequently, environmental oversight remains extremely limited. At the same time, Myanmar’s continuing civil conflict has further restricted outside inspections and enforcement.
Researchers say the Wa region has become one of Southeast Asia’s fastest-growing mineral extraction centres. Gold mining has expanded rapidly during the past decade. Meanwhile, rare earth production has also accelerated.
Chinese companies and investors are widely involved in mineral development, often working through local partners. As a consequence, mining has expanded far faster than environmental regulation.
Wa-controlled mining regions remain difficult to regulate as extraction expands beyond oversight
The political landscape further complicates the problem. Many suspected pollution sources lie beyond the effective control of Myanmar’s central government.
Instead, they operate inside territories administered by ethnic armed organisations, including the United Wa State Army. Others are located in areas controlled by different armed groups or local militias. Accordingly, identifying operators, enforcing standards and conducting independent inspections remain exceptionally difficult.
For Thailand, however, the contamination does not stop at the border. The Kok River first enters Thailand at Tha Ton in Mae Ai district, making Chiang Mai the country’s first point of exposure. Communities there rely upon the river for irrigation, fishing, tourism and household water. Therefore, environmental monitoring in Chiang Mai provides Thailand’s earliest warning that pollution has crossed the border.
Public attention has focused mainly on Chiang Rai. Yet contaminated water first reaches Chiang Mai before flowing east. The river then continues across Chiang Rai before joining the Mekong. As part of this journey, heavy metals move steadily through Thailand’s northern river system.
Chiang Mai becomes a key line of exposure as polluted water reaches Chiang Rai and the Mekong
Scientists say arsenic behaves differently from many other pollutants. Rather than disappearing downstream, much of it binds to fine sediment.
Eventually, that sediment settles along riverbeds and floodplains. During seasonal flooding, contaminated material can spread across farmland before re-entering the river. Consequently, pollution may remain in affected ecosystems for many years.
Farmers, therefore, fear that heavy metals could gradually accumulate in rice fields and vegetable crops irrigated from contaminated waterways. Fishing communities face similar concerns because arsenic and lead can accumulate inside aquatic organisms over time. Authorities continue studying contamination levels in fish and freshwater species. Meanwhile, tourism operators report increasing concern among visitors over river safety.
Chiang Rai has already experienced visible consequences. Residents have reported unusually cloudy water. Fishermen describe declining catches. Some fish have reportedly developed visible lesions. In addition, farmers remain concerned about long-term contamination of agricultural land.
Arsenic accumulates in river sediment, raising long-term risks for farming, fisheries, tourism and public health
Health experts warn that prolonged arsenic exposure presents serious long-term risks. Brief contact with contaminated water is unlikely to cause severe illness.
However, drinking polluted water or regularly consuming contaminated food may increase the risk of cancers, cardiovascular disease, neurological disorders and developmental problems. Thailand has experienced serious arsenic contamination before, making the latest findings especially significant.
The crisis now extends beyond the Kok River. The river ultimately joins the Mekong, one of Southeast Asia’s most important waterways. The Mekong supports tens of millions of people across several countries. Therefore, contamination entering northern Thailand has wider regional implications. The Mekong River Commission has already expanded monitoring across the basin.
Pollution spreads beyond the Kok River as contamination reaches the Salween, Kraburi and wider Mekong basin
Elsewhere, testing has identified elevated arsenic concentrations in the Salween River in Mae Hong Son. The Salween supports agriculture, fisheries and water supplies along the Thai-Myanmar border.
Further south, authorities have also detected elevated contamination in the Kraburi River separating Ranong province from Myanmar’s Kawthaung region. Although contamination there remains less severe than in the Kok River, the findings suggest heavy metal pollution now affects multiple international watersheds entering Thailand.
River Kok in Chiang Rai poisoned with arsenic from Wa state-controlled gold mining across the border
Golden Triangle drug lords or Wa Reds are Thailand’s enemy and it must tackle them head on, says Thaksin
Taken together, the Kok, Mekong, Salween and Kraburi rivers reveal an expanding transboundary pollution problem stretching from northern Thailand to the Andaman coast. Each river originates outside Thailand.
Consequently, Thai authorities have limited power to regulate upstream mining activities. Until broader international cooperation begins, downstream communities remain exposed to contamination generated beyond Thailand’s borders.
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