Frustrated locals staged a protest urging the government to act on the alarming air pollution clouding northern Thailand.

Some 200 protesters - including monks, doctors, and activists - gathered in front of the King Mangrai Monument in Chiang Rai province on April 10 demanding solutions to the choking smog they have been grappling with for weeks.

They also donated bottles of mineral water to firefighters battling wildfires around Thailand.

It came as the toxic haze from air pollution continues to cloud northern cities including Chiang Rai, Chiang Mai and Mae Hong Son.

Chiang Mai was given a ranking of 223 by Swiss air quality monitor IQAir today. They recorded 173 micrograms of PM2.5 particles per cubic metre of air - more than 34 times the safe levels advised by the World Health Organization (WHO).

Chiang Rai was ranked 245 with 194.6 micrograms per cubic metre of deadly PM2.5 in the air - 38.9 times the safe level.

Ponlawat Tansiri, former president of the Chiang Rai chapter of the Federation of Thai Industries, said: 'PM2.5 should be considered a regional problem since it occurs not only in Chiang Rai or Thailand, but also in Laos and Myanmar.'

He also called on government officials to discuss the matter with neighbouring countries to find a long-term solution.

Chiang Rai governor Puttipong Sirimat sent a delegation to respond to the protesters' demands.

Waradisorn On Nut, Deputy Governor of Chiang Rai, claimed the local government has already devised plans to address the air pollution, adding the forest fires aggravating the smog were allegedly caused by 'drug-related individuals.'

He said Chiang Rai had not yet been declared a disaster zone as the label would 'have an impact on other aspects', and that the current budget was sufficient to deal with the haze.

The disaster zone designation would have allowed resources to be mobilised quickly to address the hazardous PM2.5 dust levels, which have been responsible for thousands of hospital admissions.

Somkiat Puka, provincial director of the Office of Natural Resources and Environment, said 18 suspected arsonists have been arrested so far, but the fires they started were still reigniting.

In a statement, Governor Puttipong said there are plans to 'rehabilitate' Chiang Rai from April 16 to September 30 this year.

Scientists found that smog is at its worst in the country when farmers burn waste crops to cheaply clear their land between late October and April. It has been worsened in recent years by rising demand for food and agro-business lobbyists that can stifle the government's control over farmers.

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 – hampers the pollution from being dispersed naturally by wind.

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.