The cabinet on Tuesday approved a ban on maize imports from areas where farmers burn-off their fields, with enabling legislation to take effect this year.
The move is aimed at reducing the annual smog-fest, which the government blames largely on neighbouring countries.
Government spokesman Chai Wacharonke said the cabinet instructed the Commerce Ministry to prepare an order banning imported maize from areas that practice field burning, to combat the annual smoke-induced smog that sets off health alarms.
The resolution was an expression of the government's concern about air pollution caused by field burning in neighbouring countries, he said. To prove the connection, officials making the decision would compare areas of maize cultivation with hotspot maps produced using satellite imagery, Mr Chai said.
Any import bans would comply with the relevant rules of the World Trade Organization. Their imposition would, however, have to wait for passage of a planned Clean Air Act, which was expected this year, he said.
According to the spokesman, market demand in Thailand is for 8.9 million tonnes of maize annually. Domestic production is about 4.9 million tonnes a year.
Thailand currently imports about 1.6 million tonnes of maize from neighbouring countries - including 600,000-700,000 tonnes from Myanmar, 300,000-400,000 tonnes from Laos and about 100,000 tonnes from Cambodia.
More than 2 million tonnes of maize is purchased from other countries, mostly from Brazil.
Speaking after Tuesday's cabinet meeting, Prime Minister Srettha Thavisin insisted any measures to limit or ban imports from neighbouring countries must be supported by proof that these products are linked to agricultural burning.
More importantly, all these measures must strictly conform to international trade agreements with the WTO, of which Thailand has been a member since Jan 1, 1995.
He said the measures will be covered by the Ministry of Commerce's Exports and Imports Act, which aims to tackle haze pollution, particularly during the high season of agricultural burning.
Also, the PM said, the measures imposed on maize imports will also have to be in line with the clean air bill which will soon complete its passage through the House of Representatives.
Mr Srettha said that transboundary haze pollution resulting from burning practices in these neighbouring countries' crop-growing areas continues to affect Thailand, explaining why import bans and limitation measures are considered necessary.
At Tuesday's cabinet meeting, Mr Srettha said he didn't want Thailand to continue importing maize from countries where agricultural burning occurs. According to a source present at the meeting, a few cabinet ministers opposed his idea.
Deputy Commerce Minister Napintorn Srisanpang, for one, said such an import ban could never be implemented because it would violate WTO regulations unless the clean air law comes into force first.
And while Thailand aims to make other countries stop agricultural burning, Mr Napintorn said this country needs to stop burning, too.
Mr Srettha also said after the meeting in Phayao that the reason for not declaring Chiang Mai a disaster zone was due to concern that it might have affected internal trade, not just hurt the tourism sector.
On Monday, Mr Srettha posted on X that the government decided against declaring Chiang Mai a disaster zone despite its worsening air pollution out of fear that it would hurt the province's tourism industry.
"The effort that the government has made from last year to this year has helped alleviate the fine dust problems, which have fallen to one-third or two-thirds of previous levels in some areas," he wrote.
"Although Chiang Mai's weather has improved, the government will continue doing its duty," he added.
Meanwhile, a Facebook netizen who goes by the name of "Tanuwat Weraphongkamon" urged the premier to stop blaming the weather.
"The internet is currently driving the world. Do not try to lie. People from other countries travel to Chiang Mai. I volunteer to be your adviser free of charge," he wrote.
In addition, he also suggested that the premier hand out 90 face masks to at least 80% of the residents of Chiang Mai province over the course of three consecutive months.