PM2.5 reached dangerous levels in parts of the North and West on Thursday morning, while Samut Songkhram was the only province in the red zone, with unhealthy levels of smog.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 9am on Thursday that the central province of Samut Songkhram, located west of Bangkok, recorded 77.1 microgrammes of PM2.5 per cubic metre of air over the past 24 hours.
Meanwhile, 26 other provinces experienced orange levels of PM2.5, ranging from 38.3 to 69.9µg/m³.
The South and parts of the Northeast, the Central Plains and the East reported safe levels of PM2.5, with the safe threshold set at 37.5µg/m³.
The lowest level, 14.4 µg/m³, was measured in the northeastern province of Amnat Charoen.
Thursday's situation was an improvement over Wednesday morning, with 27 provinces facing unsafe PM2.5 levels, down from 33 on Wednesday.
