A toxic haze shrouded Bangkok today reaching unsafe levels in 29 areas of the capital.

Footage shows the gray mist shrouding skyscrapers in the city on Tuesday morning.

The Bangkok Air Quality Information Centre reported an average PM2.5 reading of 49.6 micrograms per cubic metre across Bangkok. While Swiss monitor IQAir recorded PM2.5 levels of 57.4 - more than 11.5 times the safe levels advised by the World Health Organisation (WHO).

State officials said there was less pollution compared to yesterday, but the pollutant levels were still unsafe.

They warned residents, especially those with respiratory diseases, to avoid going outdoors and to wear masks when venturing outside.

The agency forecasted air pollution to improve from April 18 to 20 as thunderstorms are expected to hit the region in the following days. It added that strong southerly winds were also blowing haze from the area.

Scientists found that smog is at its worst in Thailand when farmers burn waste crops to cheaply clear their land between late October and April. It has worsened in recent years by rising demand for food.

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.