Almost 6,000 hotspots were detected in neighbouring countries on Sunday, with at least 4,000 of them located in Cambodia, according to the Geo-Informatics and Space Technology Development Agency (Gistda).
The satellite images, collected by the Suomi NPP satellite, revealed 5,823 hotspots in neighbouring countries. Cambodia has the highest number, at 4,056, followed by Myanmar at 979, Laos at 622 and Vietnam at 166.
The images also showed that 601 hotspots were detected locally. Of them, 169 were in forest areas. Kanchanaburi topped the provinces with 110 hotspots visible by satellite.
The Pollution Control Department's Centre for Air Pollution Mitigation reported at 7am on Sunday that PM2.5 levels had exceeded the safe threshold of 37.5 microgrammes per cubic metre (µg/m³) nationwide, except in some parts of the South.
Gistda's Check Foon (dust checker) app also reported that by 8am on Sunday 30 provinces were experiencing orange-coded levels of dust, which signifies potential danger, especially to those with weak health.
In Bangkok, the city's Air Quality Information Centre reported dust levels of 41.9 µg/m³, with measurements ranging from 31.7 to 59.8 µg/m³ from 5–7am on Sunday.
The city's dust levels are expected to worsen during Feb 12–18, with alerts likely to come in at least 17 districts, the information centre said.
Regarding cross-border pollution mitigation, Wijarn Simachaya, president of the Thailand Environment Institute, said PM2.5 pollution has been around for a long time, particularly in the north, and has battered people's health and affected tourism.
He said the problem requires an integrated solution including a ban on slash-and-burn farming, that must involve cooperation from neighbouring countries.
Wilavan Noipa, director of the Thailand Environment Institute Foundation's Natural Resources Programme, said inter-ministerial cooperation would help tackle cross-border smog.
Meanwhile, a fire was raging on Sunday over a vast expanse of forest on the Cambodian side near the Buntad mountain range in Trat.
The fire has claimed at least a square kilometre of forest in Thailand and generated haze covering tambon Chamrak of Muang district.
According to the Paramilitary Marine Force Company 535, the fire began at least two days ago and deteriorated rapidly on Sunday.
Local authorities contacted agencies in Cambodia to raise concerns over the fire, according to Phira Eiamsunthorn, deputy governor of Trat.