Bangkok residents have been told to expect rising levels of PM2.5, which forecasters at the Pollution Control Department have said will continue to worsen until Wednesday.
The department is urging Bangkok residents to work from home until Wednesday to avoid the worst of the air pollution.
The PCD said the rising concentration of PM2.5 pollutants is caused by poor air circulation and wind.
The Bangkok Metropolitan Administration (BMA) is stepping up its inspections of all pollution sources in the capital. City Hall has also ordered schools to arrange "dust free" rooms at all kindergartens and schools under BMA's supervision.
Satellite images found 1,566 hotspots on Jan 9, 1,139 on Jan 10, and 1,023 on Jan 11.
Prime Minister Srettha Thavisin plans to raise the issue when he meets the Cambodian PM in Thailand on Feb 7.
Mr Srettha had previously said Thailand and Cambodia will together fight transboundary haze pollution.
The Natural Resources and Environment Ministry has also asked Asean's secretary-general to urge all countries in the Greater Mekong Subregion to prevent forest fires by cracking down on activities such as slash-and-burn farming.
In Chiang Mai, farmers have been encouraged to stick with just ploughing the soil to clear their rice fields instead of burning rice straw, which adds to haze pollution.
