CHIANG MAI: High pollution levels in Thailand's northern city of Chiang Mai and surrounding provinces are keeping tourists away and alarming locals, with the government on Monday urging residents to avoid outdoor activities.

For several weeks last month the city was at the top of air quality information platform IQAir's global chart on poor air quality, ahead of Lahore and New Delhi.

Chiang Mai, known for its scenic mountainous views, temples and chic cafés, received 10.8 million visitors in pre-pandemic 2019, but hotel bookings in the city have dropped to 45% occupancy, the Thai Hotel Association Northern Chapter president Phunut Thanalaopanich told Reuters on Monday. That is far short of the 80% to 90% expected ahead of this week's Thai New Year holidays, known as Songkran.

"Its impacted my business ... people aren't coming (they) can't see the view," said Sunat Insao, 53, who sells orange juice.

Addressing the deteriorating air quality in the north, Thailand's health ministry urged the public on Monday to avoid outdoor activities and wear masks that can filter particles.

Chang Mai, Thailand's third-biggest city, reached 289 on IQAir's air quality index (AQI) index in March, which measures the level of inhalable fine particles in the air.

On Monday it had eased to 171, but was still 19 times over the World Health Organization's recommended level.

"You can feel (the dust) in your face ... I clean my face, I see the pad and I was like, 'this is really, really dirty,'" said Fernanda Gonzalez, 27, who was visiting from Mexico.

Authorities have blamed a combination of forest fires and crop burning in Thailand and its neighbouring countries.

Thai Prime Minister Prayuth Chan-ocha said last week he was coordinating with Laos and Myanmar to reduce hot spots in the border area to curb transboundary haze.

Chiang Mai resident Pathsharasakon Po, 36, said she was concerned about allergies, or even cancer.

"It's getting worse and worse year by year," Pathsharasakon said.