Air quality continues to deteriorate in northern Thailand. This footage shows smoke billowing from a valley in the mountainous district of Doi Mae Salong, Chiangrai province.

The Ministry of Public Health has put Bangkok and 23 provinces on the list of the places with the highest levels of PM 2.5. Among them is Chiang Rai, the northernmost major city in the country.

The mountainous district of Doi Mae Salong in Chiangrai province shows smoke billowing from a valley close to the Thailand border with Burma. The cold atmospheric air traps pollution resulting from human activity.

In Chiang Rai city the air quality index is shown as between 133 and 174 for PM 2.5 particles over the past 48 hours.

The WHO guidance is 15 pm for 2.5 particles.