Chiang Mai – For generations, young Lahu Christians have waded chest-deep into the Kok River for baptism, submerging three times whilst their community sang hymns on the banks. This year, the ritual was canceled. The river still flows, but it now carries poison instead of blessing.

Government tests detected arsenic and heavy metal contamination in the 285-kilometre waterway, which officials believe is linked to mining operations upstream in Myanmar. The Regional Environmental Office 1 Chiang Mai has warned residents against any contact with the water, citing health risks.

“The government says if anyone goes in to swim, they’ll have allergic reactions, rashes, severe itching,” said Sela Lipo, 60, who has lived on the riverbank his entire life. “Or if you drink it and it accumulates, you’ll get diarrhoea and eventually cancer.”

In Ban Pha Tai alone, the crisis has cut off water access for more than 200 households, eliminated fishing incomes overnight, and sent weekly household water costs soaring as families scramble for alternatives.

The contamination is believed to stem from mining operations in Myanmar’s border regions, where rare earth and gold extraction has surged since the 2021 military coup. Waste flows downstream into the Kok and the Mekong, but Thai authorities cannot regulate activity across the border.

Livelihoods lost

Ban Pha Tai in Chiang Mai’s Mae Ai district comprises eight settlements with more than 200 households, mostly Black Lahu Christians. For them, the Kok River was the economic and cultural centre of community life. It was where pastors led believers into the water for baptism, where children played during holidays, and where families drew water for every daily need.

“We’ve used Kok River water to wash clothes, bathe and farm,” Sela said. “When free, we’d catch crabs and fish to share and eat. But now we can’t do that. People who fish for a living immediately lost their jobs. Those who grow vegetables near the river are afraid to eat them.”

Nicha Chalo’s retail shop, which once sold fresh goods, snacks, and souvenirs to tourists along the riverbank, now moves only cooking gas – barely enough to survive.

“Since the beginning of the year, income has disappeared by half compared to previous years,” Nicha said. Her shop once earned 40,000-50,000 baht annually (about 1,230-1,530 USD), but now she barely breaks even.

It’s been four months since Nicha has seen a single tourist boat pass by.

Recently collected data shows at least ten tourism businesses along the Kok River have accumulated losses exceeding one million baht (30,700 USD) since early 2025. Vendor stalls, riverside rafts, and souvenir shops have continuously closed.

Water scarcity looms

Beyond lost income, households now face soaring expenses for basic water needs.

Previously, the community used Kok River water for agriculture, bathing and washing clothes, whilst purchasing drinking water from trucks. A two-person household spent about 900 baht weekly on drinking water alone. Now, with all contact with the river forbidden, families must buy additional water. “Water costs have reached over a thousand baht per week,” said Saengrawee Suweerakarn, a Shan indigenous woman from nearby Ban Mai Mok Cham.

That’s during the rainy season, when families can still catch some rainwater. The burden will intensify during the dry months ahead. The community now depends entirely on two small streams flowing down from Huay San mountain for all their water needs.

“This time it is still bearable,” said Sela, the Lahu man. “But if it’s the dry season with little water, and many people still need water but there’s only one source, there’s no way it’ll be enough.”