The worst-hit province was Mae Hong Son, with 81 hotspots.
Sakon Nakhon and Ubon Ratchathani provinces were second and third with 46 and 38 hotspots, respectively, the GISTDA said, citing images from the Suomi NPP satellite.
The satellite uses a VIIRS (Visible Infrared Imaging Radiometer Suite) sensor to detect hotspots, which are caused by either forest fires or the burning of crops or weeds.
Of the total 500 hotspots, 136 were in agricultural areas, 133 in national forests, 94 in forest reservations, 77 in agricultural land reform zones, 55 in community areas and 5 were beside highways, the GISTDA said.
The agency speculated that these hotspots might have been caused by burning for agricultural activities and foraging.
From January 1 to March 14, the Northeast had the highest number of hotspots at 11,233, followed by the North (9,353) and Central (5,671).
Myanmar has had the most hotspots among Thailand’s neighbours at 2,896, followed by Laos (2,114) and Cambodia (820).
According to information at 9am on Tuesday, particulate matter less than 2.5 microns in diameter (PM2.5) in the air is reaching levels that could affect the health of people in many provinces in the North and Northeast. The Air Quality Index value in Mae Hong Son province was 100, while it climbed to 113 in Nong Khai province.
The increasing number of hotspots in nearby countries could also affect the air quality in the border areas of the North and the Northeast because the wind could blow dust particles and smog. People in those areas have been urged to take care of their health and to wear masks.
The forest fire problem has significantly affected the country, especially the economy and social system.
Soon, Thailand will fully implement the THOES-2 system. One of its missions is to explore, analyse, and monitor the upcoming or expected disaster accurately and in time. It will support related organisations with important information to plan, prevent, relieve, and solve the problem.
The GISTDA said it would continue to monitor and report the situation to related organisations to use for management. People could check the situation at the website https://fire.gistda.or.th/.