Residents of the capital were warned Wednesday by the Pollution Control Department (PCD) that the choking smog in the city had soared above levels considered safe.
Bangkokians have been suffering from harmful levels of dust in the air since last week.
The airborne particulate matter surged above the safety limit of 50 microgrammes per cubic metre (µcg) over a 24-hour average in many areas of Bangkok, a level which could endanger people's health, the department said.
Levels of particulate matter of 2.5 microns or less in diameter (PM 2.5) were measured at 72 µcg along Intharaphithak Road in Thon Buri district; 61 µcg in Bang Na district; 60 µcg in Wang Thonglang district; 53 µcg along Lat Phrao and Rama IV Roads; and 52 on Phaya Thai Road, according to the department.
Airborne particulate matter also increased on Intharaphithak and Phaya Thai roads.
Department director-general Sunee Piyapanpong suggested again that people, particularly those suffering from respiratory and heart ailments, should wear face masks to avoid breathing in ultra-fine dust particles.
However, normal face masks do not work effectively and apparently the KN95 standard mask is required.
Also Wednesday, Srisuwan Janya, president of the Stop Global Warming Association, called on the government to declare Bangkok a pollution control zone to deal with the harmful dust particles.
More vehicles on the roads have been a major cause of an increase in dust in the capital but City Hall assured the situation will "permanently improve" in 11 years with the launch of many different modes of public transport.
Suwanna Jungrungrueng, the Bangkok Metropolitan Administration's (BMA) deputy clerk, said vehicles, particularly those with diesel engines, played a crucial role in the city's air pollution problems.
At least 25% of all vehicles in Bangkok have diesel engines, or 2.4 million, she said.
Also, the total number of vehicles in Bangkok is now about 9.7 million, or 4.4 times higher than the road capacity while around 500,000 new vehicles are registered in the capital each year.
Ms Suwanna said it was obvious vehicles are the main factor contributing to the city's air pollution.
She said cleaning measures would help reduce the harmful particles in the air.
Therefore, roads and streets in dust-prone areas would be cleaned daily instead of weekly. City Hall will also ban construction work at night to bring down dust levels, Ms Suwanna added.
"In the future, all modes of mass-transit systems will be launched across Bangkok, particularly electric trains in 2029 [in 11 years] This will help alleviate traffic congestion substantially," she said, adding that less vehicle use will result in lower dust levels.
"Also, a measure regulating vehicles in city areas based on the numbers of their licence plates will be implemented similar to that in Paris, France," she said.
The Thai Meteorological Department's forecast on Wednesday said the temperature in Bangkok will drop by 1-2C in the morning while a lack of wind will increase the level of airborne particulates.
However, the situation will improve from later in the day, said Kamol Promasakha na Sakolnakhon, director of the TMD's Meteorological Radar and Satellite Data Analysis Division.
The city's haze woes prompted Prime Minister Prayut Chan-o-cha Wednesday to instruct the Department of Royal Rainmaking and Agricultural Aviation to carry out artificial rainmaking to help eliminate dust particles in the air across Bangkok.
Rain making will take place soon when weather conditions are suitable.
The department also asked the public and private sectors to refrain from rubbish burning and construction activities.
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