While the level of PM2.5 has declined in the capital, the hazardous dust has hit Khon Kaen, Phrae and Nakhon Sawan, with the worst air quality recorded in Khon Kaen.
The Pollution Control Department (PCD) reported yesterday morning there were no hazardous levels of fine dust in greater Bangkok, with PM2.5 readings at 18-44 microgrammes per cubic metre (µg/m³) over the last 24 hours.
Levels of particulate matter 2.5 micrometres and less in diameter (PM2.5) fell in almost all air measurement areas in the city and surrounding provinces.
The lowest level, 18 µg/m³, was reported in Bang Na sub-district of Bang Na district in Bangkok and the highest, 44 µg/m³, on Lat Phrao Road in Wang Thonglang district of the capital. The government puts the safe threshold at 50 µg/m³.
Thai soldiers took their high-powered water cannons to the very top of Baiyoke Sky Hotel and sprayed the Pratunam market and shopping area.
Meanwhile, the situation in Khon Kaen, a major province in the Northeast, has been getting worse.
Khon Kaen governor Somsak Changtrakun organised to spray water from a 37-metre crane of a fire truck opposite Khon Kaen University yesterday as the thick cloud of dust in Muang district alarmed residents.
He led officials in the latest effort to deal with PM2.5 after the area was found to have a very harmful level of the dust (79 µg/m³).
This was calculated as the average of a 24-hour period. It made Khon Kaen the province with highest level of PM2.5 for the second consecutive day.
"The haze is visible to the naked eye," Mr Somsak said, adding it was most noticeable above Nong Khot pond in tambon Ban Pet in Muang district.
"It's so obvious that people are in a state of panic."
On Tuesday, Mr Somsak helped workers clean a section of a road in front of Khon Kaen railway station, which is under renovation, hoping to curb the dust levels.
The province is also suffering from PM10, larger dust with a diameter of 10 micrometres, according to the Pollution Control Department. Construction sites are its major source.
The PCD measured the levels of PM10 in the province yesterday at between 70 µg/m³ and 133 µg/m³, compared with the safety standard of 120 µg/m³.
The situation is expected to improve next week as rain is forecast to soak the Northeast, Mr Somsak said, citing prognostications by the Meteorological Department. However more needs to be done, he said.