More than 50 Thai-registered companies are importing critical minerals from Myanmar despite a widening cross-border water pollution crisis linked to mining operations upstream, according to an investigation by Mongabay. The trade includes antimony, tungsten, copper, lead, manganese and tin, much of it passing through Thailand before being re-exported to China. For those living in or travelling around northern Thailand, the issue has direct practical implications for river use, irrigation areas and locally sourced food in affected border provinces. At least six Thai rivers have been found to contain heavy metals linked to mining in Myanmar: the Kok, Sai and Ruak, which feed the Mekong; the Mekong itself; the Salween along the Thai-Myanmar border; and the Kraburi River in Ranong province. Thai authorities have identified arsenic, cadmium, lead and other contaminants. The pollution has affected food and water security for tens of thousands of people in Thailand, while farming land and farmers in Chiang Rai have reportedly been contaminated. Trucks cross at Pheung Khleung On June 26 the reporter observed at least 13 double-trailer trucks were waiting at the Pheung Khleung border crossing in northern Thailand, one of the few legal overland routes for minerals coming from Myanmar. Thai military personnel overseeing the trade had granted Mongabay permission the previous day to document hundreds of tonnes of antimony expected to arrive from Karen state for Tak province, around 200 kilometres south of Mae Sot. Reporters were told they could not photograph soldiers or the minerals themselves. The gates opened at 10am, allowing the first truck carrying antimony to enter Thailand. Antimony is a silvery mineral used in bullets, bombs, armour, semiconductors and other defence, aerospace and technology industries. Workers transferred one-tonne bags said to contain antimony ore and stacks of processed antimony ingots from Myanmar vehicles to Thai trucks. The Thai loads were covered with tarpaulins, checked briefly by soldiers and sent towards Mae Sot. A driver told Mongabay the shipment had travelled for two hours from a mining site near Three Pagodas Pass, which links southern Karen state to Kanchanaburi province. He declined to identify the company he worked for. Two sources familiar with Myanmar's extractive industries said antimony mining had become industrialised across Karen state, including areas controlled by the Karen National Union. Much mineral processing is carried out in Myawaddy, which is controlled by forces allied with Myanmar's military regime, and the sources said processing can be more environmentally damaging than mining. An anonymous trader said Thai buyers focus on mineral purity, while mines are often identified by the names of landowners leasing sites to Chinese investors. The trader said the trade at Pheung Khleung had expanded sharply since last year, with a dramatic rise since 2025. Imports rose as contamination spread Satellite analysis by the US think tank Stimson Center has identified 2,214 mining sites in Myanmar since 2015, with more than half opening after the 2021 military coup. In the first nine months of 2025, Thailand imported 105,752 tonnes of antimony, tungsten, copper, lead and manganese from Myanmar, mostly as ore, according to documents seen by Mongabay. The shipments were worth more than 13.9 billion baht - more than double the value and volume of all Myanmar mineral imports in 2024. Tin imports also appear to have increased, although available data were unaggregated and incomplete. Mongabay said it was unclear whether the datasets it received were complete or current. The Thai Customs Department did not respond to requests for updated figures or clarification on the risk of falsely labelled minerals. The Pollution Control Department, which is testing affected rivers, also did not answer questions about which minerals may be responsible. Phattarapong Leelaphat, a People's Party MP for Chiang Mai and chair of the Parliamentary Sub-Committee on Transboundary Water Pollution, said the government should improve customs data and use Section 104 of the 2017 Minerals Act to regulate or halt imports until they can be shown not to damage Thai rivers. "We don't know which mine [the minerals] actually come from," he told Mongabay. He also questioned whether customs officials had the technology to establish whether cargo declared as tin or antimony might in fact be rare earths or other minerals. For residents and visitors in northern river communities, the case underlines the importance of following local guidance on water use, fishing and produce from affected areas. The pollution concerns are concentrated around waterways and agricultural communities. Supply chains lead on to China Mongabay tracked 12 importing companies in Chiang Mai, Chiang Rai and Tak during June. Nearly half of the Thai firms listed as importers are based in those northern provinces. The official data covers minerals entering through legal crossings such as Pheung Khleung and river ports in Chiang Rai. Traders said illicit smuggling routes are also believed to operate along the border. Much of the mineral trade is then sent to China via Laem Chabang Port in Chonburi, traders told Mongabay. Minerals from Shan state can also travel down the Mekong through the Golden Triangle Special Economic Zone before reaching river ports in Chiang Rai. Songphon Teampantunan, director of Thepthrni Business Mining Company, said his firm has operated two antimony mines in Karen and Mon states since 2010. He denied his mines were responsible for pollution and said the company had imported between 1,000 and 3,000 tonnes of antimony a month for years. He said rising logistics costs caused by Myanmar's civil war had been partly offset by antimony prices more than doubling since 2021. He also said many newer Thai and Chinese mining firms had entered the sector, alleging that some Chinese companies used mining to launder money from phone scams. Other Thai importers told Mongabay they had little knowledge of where their minerals were mined. Waraporn Thepsan, general manager of Mae Sot-based Far Far Shipping Service Limited Partnership, said brokers handled supplies from Myanmar and that most of her firm's antimony and tin was re-exported to China, with some shipments going to Japan and Spain. "I never get information about the companies or the mines that are involved on the Myanmar side," she said. Pictures courtesy of Mongabay Join the discussion? 2 October 2026
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