The amount of particulate matter in the air was at health hazardous levels throughout Bangkok on Friday morning, with the exception of Chom Thong district. Nong Khaem district was worst affected, the Bangkok Metropolitan Administration said.
Online reports from the BMA showed hazardous levels of particulate matter in most locations where it measures air quality.
In addition to Nong Khaem, serious levels were detected in Prawet and Bangkok Yai districts.
The Pollution Control Department attributed the pollution level to stagnant weather which trapped emissions from vehicles.
People were advised to stay indoors or wear face masks if going out. The problem could be worse on Saturday, especially on the streets, it said.
Bangkok governor Aswin Khwanmuang attributed the pollution to exhaust emissions in areas of traffic congestion, railway and condominium construction, road works and dry season weather.
To help alleviate it, he ordered district officials to clean roads, spray water, encourage people to use public transport instead of their cars, and increase green areas.