The National Hazardous Substances Committee (NHSC) on Monday ruled in favour of consumer groups to keep its ban on the use of paraquat and chlorpyrifos in Thailand's agricultural sector.
Twenty out of the 27 members of the committee voted to maintain the ban, while four voted against and three abstained.
Speaking after the committee meeting, Industry Minister Suriya Juangroongruangkit said the NHSC would not revisit the decision in the future.
"This decision is final. There should not be any further request to reconsider our resolution because the committee has made it clear that these chemicals are highly dangerous to our health and many other countries have also banned their use," he said.
The committee also ordered the Ministry of Agriculture to find alternatives to help farmers cope with the financial impact of the ban.
Monday's ruling effectively ended a years-long effort by proponents of the chemicals to have the ban revoked.
The NHSC had voted on Sept 28 last year to ban the use of paraquat and chlorpyrifos, as well as to restrict the use of glyphosate in the agricultural sector by April 1.
The deadline was moved to June 1 following the push by pro-chemical groups, who petitioned the NHSC to further delay the enforcement of the ban.
Apai Sutthisang, of the Ministry of Agriculture and Cooperatives, said the ministry has prepared several alternatives which farmers could use in lieu of the toxic chemicals.
However, he also said the ban would increase the financial burden of farmers, as alternatives to the banned chemicals are higher. "Without them [the chemicals], their operating cost would go up by 30-40%," he said.
"But we will ask the Ministry of Commerce to encourage better market prices for crops which are grown organically, to offset the higher cost of investment," he said, adding the ban of toxic chemicals should encourage farmers to embrace organic farming.
By June next year, the Ministry of Public Health plans to set a limit for paraquat and chlorpyrifos residues in food ingredients grown domestically, as well as imported raw materials such as wheat and maize.