KAN Air cancelled a Chiang Mai-bound flight yesterday after the haze problem in Mae Hong Son rose to high levels in the Upper North, resulting in visibility being restricted to less than 1,000 metres, Mae Hong Son Airport chief Weerawat Thadong said.

Weerawat said the 12pm flight cancellation was a safety precaution.

The noon cancellation resulted in some affected passengers being transported to the city in vans, while others postponed their travel plans.

The level of small particulate matter up to 10 microns in diameter (PM10) recorded in Mae Hong Son was 233 mcg in the morning, and rose to 244 mcg at 5pm.

Anything above 120 micrograms is considered unsafe.

Meanwhile, Mae Sai district in Chiang Rai province recorded a yearly high of 248 mcg at 5pm yesterday, according to the Pollution Control Department.

That prompted an urgent meeting between Thai and Myanmar officials, which ended with a call for stricter bans on outdoor burning on both sides.

The other northern provinces with PM10 levels beyond the safety level yesterday were Lampang, Phayao, Phrae, Nan and Tak.

This is despite the fact that the public is reportedly cooperating with the northern region's 60-day outdoor burning ban (February 15-April 14).

Captain Chonlathai Rattanaruang, commander of the Chiang Rai-based Navy patrol unit on the Mekong River, sent men to join local officials in Chiang Saen district in the fight against haze, with water trucks used to spray vapour into the air.

Meanwhile, firefighters in Prachuap Khiri Khan's Hua Hin district yesterday adjusted their plans to tackle a fire at Kaeng Krachan National Park.

The forest fire started three days ago and has destroyed more than 1,000 rai (160 hectares) of forestland.

They shifted from solely trying to put out the flames to creating firebreaks and trying to put out the flames.

Poachers were suspected to have started the fire as traces of a bonfire and the butchering of wildlife were found at the park, an informed source reported.