The Bangkok Metropolitan Administration (BMA) on Wednesday decided to reopen 437 schools on Thursday after air quality in the capital improved slightly.
Pol Capt Pongsakorn Kwanmuang, a BMA spokesman said all 437 city schools ordered to close for one day on Wednesday will reopen.
"The air quality in Bangkok has improved to a level at which we can order schools to reopen. Only 12 areas showed high levels of [particulate matter] PM2.5 and we expect the situation to improve from tomorrow as weather and wind will help disperse dust," said Pol Capt Pongsakorn.
The BMA, however, will provide air purifiers for schools located in areas with high levels of PM2.5.
The BMA also adjusted work hours of its officials to 10am to 6pm from 8.30am to 4.30pm, in a bid to reduce traffic congestion -- a major cause of air pollution.
Meanwhile, Deputy Prime Minister Prawit Wongsuwon will on Thursday chair an urgent meeting to decide on more concrete measures to curb PM2.5 in Bangkok and upcountry.
Natural Resources and Environment Minister Varawut Silpa-archa on Wednesday hinted that the government might introduce tough measures to reduce PM2.5.
"I have to apologise if the new measures will cause inconvenience to people," he said, without elaborating.
A proposed ban on personal car use, which was revealed by Prime Minister Prayut Chan-o-cha on Tuesday, is being considered by the government.
In Bangkok, Mr Varawut said, 76% of PM2.5 is caused by traffic.
But enforcing new regulations on car use requires a close look at many details and they must be "right and acceptable", Interior Minister Anupong Paojinda said.
The levels of PM2.5 in Bangkok and its vicinity have exceeded the permissible "safe" threshold of 50 microgrammes per cubic metre (µg/m³) since early this month. The government reportedly hinted on Tuesday that it will introduce harsh measures if the readings exceed 100 µg/m³.
Phitsanulok province has been also shrouded by PM2.5, which on Wednesday was measured at between 57 and 92 µg/m³. The bad air has, since Jan 1, pushed the number of hospital patients suffering ultra-fine dust exposure symptoms to over 3,500, according to provincial public health officials.