By Friday, the level of PM2.5 pollutants – cancer-causing microparticles small enough to enter the bloodstream through the lungs – hit 108 micrograms per cubic metre, according to IQAir.
The World Health Organisation recommends 24-hour average exposures should not be more than 15 for most days of the year.
Bangkok authorities said this week schools in areas with elevated levels of PM2.5 could choose to close.
By Friday morning, 352 of the 437 schools under the Bangkok Metropolitan Authority had shut their doors, affecting thousands of students.
The figure was the highest since 2020 when all schools under the city authority closed because of air pollution.
Interior Minister Anutin Charnvirakul on Thursday ordered a ban on stubble burning – intentionally burning leftover crops to clear fields – with those responsible risking legal prosecution.
Prime Minister Paetongtarn Shinawatra, who is currently attending the World Economic Forum in Switzerland, called for tougher measures to tackle pollution on Thursday, including limiting construction in the capital and seeking co-operation from nearby countries.
Neighbouring Vietnam and Cambodia’s biggest cities also ranked in IQAir’s top 10 most-polluted major cities globally on Friday, with Ho Chi Minh City reaching second and Phnom Penh fifth.
Cambodia’s Environment Ministry spokesman Khvay Atitya told reporters on Thursday the air quality in the country was within safe levels.
“Other countries have their own standards. Cambodia has our own standard to determine the air quality,” he told reporters, adding that authorities had not issued any emergency measures.
- Agence France-Presse