More than 600 residents of Chiang Mai and Chiang Rai provinces embarked May 31 on a roughly 68-kilometer, six-day ‘peace walk’ to demand that the Thai government take action on the river pollution crisis that has seen Thai rivers polluted with heavy metals.
The ensemble of affected residents, civil society groups, monks and students marched from Tha Ton subdistrict in Chiang Mai to the city of Chiang Rai in northern Thailand, reaching their destination on June 5, World Environment Day.
For more than a year, Thailand’s Pollution Control Department has reported dangerous levels of arsenic, mercury, cadmium and other heavy metals in rivers across northern Thailand, with mining operations across eastern Myanmar suspected to be responsible for the pollution.
“We are walking because our rivers are slowly dying,” Pianporn Deetes, executive director of the Rivers and Rights Foundation, which helped to organise the peace walk, told Mongabay by phone. “Toxic contamination from unregulated mining upstream is already affecting water, fish, food, livelihoods, and public health. We do not want to wait until more people become sick. This is an emergency.”
Pianporn said the walk (42 miles) was about taking collective action to share information, document impacts and build public pressure in a bid to force the government to address the issue, which Pianporn said has, so far, been lacking.
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There is no such thing as a green transition built on poisoned rivers and sacrificed communities. Companies must conduct due diligence throughout their supply chains and ensure that the minerals they use are not linked to environmental destruction or human suffering.
Pianporn Deetes, executive director, Rivers and Rights Foundation
“Monitoring has improved, but action has not matched the scale of the crisis,” she said. “We need urgent diplomatic engagement with neighbouring countries, stronger health monitoring, transparency, and action to stop contamination at its source.”
Contamination in the Kok River, which flows 300 km (186 miles) from Tachileik in Myanmar’s Shan State into Mae Ai district, Chiang Mai before reaching the Mekong River by way of the Sai and Ruak rivers, began last year. It has since unfolded into an ongoing national public health crisis. Health authorities in Thailand found arsenic in the bodies of residents living near the Kok River.
Heavy metals have since been found in the water and fish of the Kok, Sai, Ruak and Salween rivers, as well as in the sediment of the Mekong River. More than 70 million people across Cambodia, Laos, Myanmar, Thailand and Vietnam, along with a wide range of endangered species, all depend on the Mekong River Basin for everything from drinking and bathing water to fishing and farming.
In June 2026, Thailand’s National Health Commission Office and the Faculty of Public Health at Chiang Mai University released findings from a rapid health assessment that surveyed 424 people living in Chiang Mai and Chiang Rai.
The study found that those worst affected were farmers earning less than 5,000 baht (roughly US$150) per month, with 70 per cent of respondents altering their water consumption habits and reported spending as much as 2,600 baht (~US$80) monthly to secure clean water. Of those surveyed, 63 per cent told researchers the pollution had resulted in average monthly income losses of 1,200-1,300 baht (US$36-US$40).
The continued spread of contamination through these previously clean river systems stems from unregulated mining activity in Myanmar, notably in areas controlled by ethnic armed groups that operate outside of territories held by the country’s military government, according to analysts.
Research from U.S. think tank the Stimson Center has identified 2,675 mines extracting a mix of gold, rare earth elements and other critical minerals across mainland Southeast Asia, 843 of which are operating in the Mekong River Basin across Myanmar and Laos between 2015 and 2026. Of those 843 mines, nearly a third opened in the last two and a half years.
Minerals for China, pollution for Thailand
While the environmental impacts of these mines have reached across borders, impacting communities in various parts of northern Thailand, efforts to address the ongoing pollution crisis have been stymied by the conflict in Myanmar, where mining is both a consequence and driver of fighting.
The war between Myanmar’s military government and the revolutionary forces seeking to overturn the 2021 coup has birthed a new mining boom, with many factions — especially ethnic armed groups in the country’s border regions — turning to mining as a means of financing the fight.
While some mines operate in territory held by groups, like the Karen National Union and the Karenni Nationalities Defense Force, are supporting the People’s Defense Forces in their struggle against the Myanmar military, the majority of mines suspected of polluting Thai rivers are found in parts of Shan State held by the United Wa State Party and the National Democratic Alliance Army. These two groups, which get strong backing from China, have agreements with Myanmar’s military and are not fighting for revolution.
This has rendered solving the transboundary pollution issue more challenging for the Thai government, which does not formally engage with the ethnic armed groups that currently control the majority of mining operations along Thailand’s border.
On May 7, Lalida Periswiwatana deputy spokesperson for the Thai Prime Minister’s Office issued a press release stating that the government established a working group to monitor the contamination problem in the Kok River since October 2025 and has been continuously coordinating with other countries.
“The Ministry of Foreign Affairs has sent teams to neighbouring countries to discuss concrete solutions under international cooperation to mitigate the impact on this important river in the region,” the press release said.
Mongabay sent questions to the Ministry of Foreign Affairs seeking clarification on which countries had been visited and what the outcomes were, but to date, no response has been received.
Many of the newer mines springing up across Myanmar are extracting heavy rare earth elements, notably dysprosium and terbium, which are needed for the manufacturing of permanent magnets used in everything from green energy to artificial intelligence, along with military technology. The global market for rare earth elements is predicted to reach US$15.8 billion by 2030, up from US$8.1 billion in 2024.
China’s control over some 90 per cent of the world’s rare earth processing capacity has seen the country offshore the extraction process to places like Myanmar, which is thought to account for roughly 60 per cent of China’s heavy rare earth supply. According to publicly available Chinese customs data, some 36,000 metric tons of rare earth oxides and compounds, valued at more than US$944 million, were imported from Myanmar in 2025 alone. However, much more is thought to enter China through informal channels.
“China is a major beneficiary of the rare earth and critical minerals supply chain,” Pianporn of Rivers and Rights said. “It should ensure full traceability, prevent imports linked to environmental destruction, and help address the impacts of mining that are contaminating rivers across the region.”
Chinese Embassy responds to demonstrators’ walk
The Chinese Embassy in Bangkok provided a statement on the pollution issue from the embassy’s spokesperson on May 31.
“We have noted that recent test reports released by the Thai government and relevant authorities show that the water quality of the river meets safety standards in general,” the statement said. “China has been supporting both Thailand and Myanmar in strengthening communication and coordination, conducting investigations in an objective, scientific and responsible manner, and resolving the issue through friendly consultation.”
Thai netizens took to Facebook to criticise the embassy’s statement, noting that China’s demand for rare earth elements is fueling the mining operations that have poisoned Thai rivers.
Questions sent by Mongabay to the Chinese Embassy in Bangkok regarding the peace walk and China’s role in the mineral trade with Myanmar went unanswered.
On June 5, the embassy posted on its official Facebook page acknowledging the demonstrators’ walk to Chiang Rai, noting that a collaborative team is being formed between Myanmar and Thailand to address the water pollution via a joint audit.
“The Chinese government has always placed utmost importance on protecting the environment and ecosystem,” the embassy’s post read. “Not only is it committed to domestic green development, but also requires Chinese enterprises stepping out into the global market to give utmost importance to protecting and complying with environmental regulations.”
The embassy added that Chinese business will not sacrifice the environment for economic gain and that violations will be taken seriously.
“There is no such thing as a green transition built on poisoned rivers and sacrificed communities,” Pianporn said. “Companies must conduct due diligence throughout their supply chains and ensure that the minerals they use are not linked to environmental destruction or human suffering.”
This story was published with permission from Mongabay.com.
