The government is carefully monitoring the spread of the smoke haze from Indonesia's Sumatra island that has already hit districts in Narathiwat, Songkhla and Satun provinces, Deputy Prime Minister Plodprasop Suraswadi said on Tuesday.
Mr Plodprasop said the smog level had not yet reached a level harmful to public health. It was still at a medium to high level.
The government has made preparations to cope if the situation worsens. These include artificial rain making in affected areas if necessary, he said.
The Defence Ministry will take aerial images of the area to compare with satellite images to identify where the wind was blowing the smoke to from the annual burning-off fires in Indonesia.
The Public Health Ministry's Pollution Control Department will measure the air pollution daily. The public will be kept well informed, he said.
Public Health Minister Pradit Sintawanarong said provincial offices in seven Southern provinces were instructed to closely monitor the spread of the smoke haze from Indonesia.
In each province, masks were being stockpiled to distribute to the public if the air quality gets worse. About 500,000 masks were already held in Songkhla for possible distribution.
A reporter in Narathiwat said the the smoke and smell already covered 13 districts of the province.
The haze was worse in the early morning and the evening, when visibility was down to only 300-400m. After sunrise the air slowly improved
People living near forests were more affected than people living in town centres.
Singapore has been hit the hardest since June 17 with a smoky-smelling haze due to pollution from forest fires in Indonesia's Sumatra island spreading to neighbouring countries. Malaysia also face similar situation but at lower degree and now the haze has spread to Thailand.
Southeast Asia's haze problem hit its worst level in 1997-1998, causing widespread health problems and costing the regional economy billions of dollars as a result of business and air transport disruptions.