Thailand's junta chief gave the smog-hit northern city of Chiang Mai seven days to crack down on spiraling pollution Tuesday, which has seen the tourist hotspot choke on Asia's most toxic air this week.
The city has far eclipsed other notorious pollution hotspots since Sunday, with the level of dangerous microscopic particles known as PM2.5 peaking at 480 according to the Air Quality Index. Any level over 300 is classed as "hazardous".
By contrast, the smog-hit Indian capital New Delhi peaked at 228, while Beijing reached only 161.
The pollution crisis in Chiang Mai has seen residents, street vendors and even monks donning surgical face masks and at least two universities have cancelled classes.
Crop burning during the dry season has long been blamed for poor air quality, but the smog has been exacerbated by growing industrialization and rising numbers of vehicles on the roads.
Prayut Chan-O-Cha, on a visit to Chiang Mai, demanded a clampdown on crop burning.
"I want to reiterate that the problem of hotspots (crop burning areas) must be solved in seven days," said the junta leader, who is angling to become the elected civilian prime minister.
"Nobody should ignite fires in the forest," he said.
Crop burning is normally restricted for two months in the dry season to try to curb pollution, but it remains widespread.
However, Olivier Evrard, a Thailand-based specialist for the Institute of Research for Development, said crop burning was not the only culprit.
"The government has encouraged the population to buy more vehicles and coal plants are still running at full speed," Evrard said.
A total of nine provinces are affected by the smog as the northern city of Chiang Rai prepares to host a meeting of regional finance ministers.
The seasonal duration of the haze, which used to last for about three months, has now increased to six months, according to Chaicharn Pothirat, a lung disease specialist at Chiang Mai University's Faculty of Medicine.
The long-term effects include an increase in respiratory and cardiovascular diseases, he said, adding that he is skeptical the government has any "long-term plan" good enough to tackle the problem.
"They show reporters, they fly to Chiang Mai ... but ... it does not clearly improve the situation," Chaicharn told AFP.
Earlier this year, the Thai capital Bangkok was also hit by bad smog, which led to school closures for three days.