Air pollution from agricultural fires continues to cloud northern Thailand - making it the worst country in the world for smog this morning.

Footage shows a choking orange haze blanketing Chiang Rai province on March 27, with the toxic soup reducing visibility to under a kilometre.

Locals who ventured outside reported a burning sensation in their eyes and noses, while those with respiratory illnesses felt their symptoms worsen.

Chiang Mai - once one of the most popular travel destinations - now faces having its tourism industry decimated by air pollution that politicians are unable or unwilling to solve due to its connection to the lucrative agricultural industry.

The Pollution Control Department said PM2.5 dust readings in Chiang Rai were at 232 micrograms per cubic metre. The province's Mae Sai district saw an alarming 542 micrograms per cubic metre reading.

The safe PM2.5 threshold in Thailand is 50 micrograms per cubic metre.

Local organisations on March 26 tried to dissipate the carcinogenic fine dust by using fire trucks to spray water in neighbourhoods. Firefighting teams also extinguished forest fires from neighbouring Myanmar along the Mae Sai border.

Mae Sai residents are planning to gather at the district office today to urge authorities to take swift action against air pollution.

Dr. Suwannachai Wattanayingcharoenchai, director-general of Thailand's health department, told local media: 'Exposure to long-term and excessive PM2.5 will finally cause internal inflammation, damage to lung cells, cardiovascular diseases and cancer.'

Scientists found that the smog in Thailand is at its worst when farmers burn waste crops to cheaply and quickly clear their land between late October and April. This is combined with high numbers of polluting cars on the road and large construction projects across the capital.

The seasonal lack of wind and rain, combined with a winter low-pressure system in which cold air is trapped closer to the ground by warm air above – prevent the pollution from being dispersed naturally.

The Thai government has been criticised for failing to tackle the country's air pollution crisis, with bizarre measures such as spraying water into the air and giant purifiers having no impact.