Bangkok Airways has extended its cancellation of flights to and from the northern border province of Mae Hong Son until at least March 24 due to poor visibility caused by haze and smog.

The airline earlier cancelled flights to Mae Hong Son between March 14-16.

Sunthorn Kanthamala, an official at the Mae Hong Son meteorological station, said the temperature at the airport on Sunday morning was 19 degree Celcius and visibility was only 1,600 metres, considered hazardous for flying.

Visible infrared imaging radiometer suite (VIIRS) satellite images at 1.36am showed 100 hotspots - signs of a forest fire - in Mae Hong Son, 83 in Chiang Mai, 54 in Phayao, 49 in Tak, 38 in Nan, 37 in Chiang Rai, 31 in Lampang, 24 in Phrae and 20 in Lamphun provinces.

Of the 100 Mae Hong Son hotspots, 19 were in Mae Sariang, 12 in Mae La Noy, 22 in Khun Yuam, 13 in Muang, 14 in Pang Mapha and 20 in Pai districts.

The PM 2.5 reading was 83 microgrammes per cubic metre of air in tambon Chong Kham of Mae Hong Son district on Sunday morning.

Firefighting units have been deployed to combat wildfires in mountainous and forested areas of Mae Hong Son to reduce hotspots.