The move came after the district, which borders Myanmar, was engulfed in choking yellow smog. PM2.5 readings there surged to 542 milligrams per cubic metre (μg/m3) on Monday – more than 10 times above the safe limit.
Chiang Rai’s severe air pollution is blamed on forest and agriculture fires burning across the North and over the border in Myanmar.
As of Tuesday, PM2.5 in Chiang Rai's Muang district measured 407μg/m3, according to the Pollution Control Department.
Thailand’s safe limit for PM2.5 – fine-dust pollution linked with early death from heart and/or lung conditions – is 50μg/m3.
Locals on Monday submitted a letter to Mae Sai district chief Narongpon Kidarn, demanding short and long-term solutions to the PM2.5 crisis, including negotiations with neighbouring countries and placing PM2.5 on Asean's agenda.
They also accepted donations of equipment and drinking water for firefighters who are battling forest fires in the province.
Sawetyont Srisamut, vice president of the Chiang Rai Chamber of Commerce, said the province suffered severe air pollution every year.
He pointed out that Thailand now has satellites and technology that can detect hotspots and fires as they occur within its own borders and in neighbouring countries.
"Hence, the government should negotiate with neighbouring countries on this issue," he said.
Satellite images confirm that most of the fires are being lit in Myanmar, Laos and northern Thailand.
Trasak Srithiphan, an adviser to Chiang Rai Chamber of Commerce, said air pollution this year was more severe than the crisis of 2011.
He said the situation would get even worse if the government and authorities did not tackle the problem.
"We hope the government and related agencies are paying attention to this issue," he said.
Narongpon said the problem came from smoke blowing across the border, adding that there are few hotspots in Chiang Rai as local farmers are not burning their fields for harvest. He also advised locals to take care of their health following a rise in reports of breathing difficulties.
Watcharapong Khamla, a public health doctor in Chiang Rai, said the number of residents suffering respiratory problems in the province was high but falling.
March 12-18 saw 4,847 people treated for breathing problems while that figure dropped to 3,478 last week (March 19-26).
Mae Sai district recorded 472 respiratory cases from March 12-18 and 372 last week.
He said most patients had nasal irritation and sore throats and were given medicine at hospitals to treat their symptoms at home.
Chiang Rai has sufficient hospital beds for patients who develop more severe symptoms due to the smog, he added.