The National Environment Board (NEB) on Wednesday ordered all 17 provinces in the North to stop burning activities until the end of April.
The Department of Pollution Control said the level of PM2.5 had reached as high as 225 microgrammes per cubic metre (μg/m³) in some spots early this month.
Also, the number of hotspots from January to March jumped to 56,439 points nationwide, with 31,719 in the North.
The NEB has come up plans to deal with the PM2.5 pollution, including enforcing a zero-burning policy in both forest and agricultural zones in the 17 northern provinces.
The NEB also banned purchases of sugar cane harvested by burning methods; limited the number of trucks allowed to enter urban areas; planned to make artificial rain and set up PM2.5-free spaces.
Kasetsart University said the main source of PM2.5 smog in Bangkok is from burning activities outside the city.
