Bangkok Airways has announced the suspension of its morning flights between Chiang Mai and Mae Hong Son until at least Saturday as haze continues to plague northern provinces.

According to the airline, two morning flights between the two provinces -- PG351 to Mae Hong Son that was due to depart on 9.20am, and PG352 to Chiang Mai scheduled for 10.35am -- were cancelled on Thursday.

The suspension was deemed necessary as both airports were shrouded by thick haze which reduced visibility to two kilometres.

The aircraft used to service the route, an ATR-72, requires a minimum visibility of 6km to be able to take off and land safely.

The airline said 10 morning flights have been cancelled over the past five days, and the suspensions will continue until tomorrow because of the poor visibility.

In Mae Hong Son Thursday, the level of PM 2.5 was around 96 microgrammes per cubic metre (µg/m³), which exceeded the safe threshold of 50 µg/m³.

Authorities said that 279 forest fires had been detected in Mae Hong Son between Jan 1 and March 12, as opposed to 141 during the same period last year.

Deputy Prime Minister Prawit Wongsuwon visited Chiang Mai to follow up on efforts to reduce haze in the North.

"The major cause was forest burning," said Gen Prawit. "Ways must be sought to make sure there will be no forest burning in the future."