The PM2.5 level – airborne particulates 2.5 microns or less in diameter – was at 55 micrograms per cubic metre of air on Thursday. The safe level in Thailand is 50.
Thananchai Wannasuk, director of Regional Environmental Office 16 based in Songkhla, said the smoke that first appeared in the southern province on Wednesday came from the Indonesian island of Sumatra.
The area of Hat Yai in risky smog conditions has a 30-50-kilometre radius. Residents have been advised to stay indoors as much as possible and to wear face masks when going out.
Thananchai said they should be alert to coughing, eye irritation or difficulty breathing.
He has briefed in writing the provincial natural-resource and environment offices in Songkhla, Satun, Pattani, Yala and Narathiwat, nearby Regional Environmental Offices 14 and 15, and the Ministry of Natural Resources and Environment.