The Department of Special Investigation (DSI) has seized almost 150,000 litres of glyphosate, which is a controlled substance, as part of its investigation into the smuggling of the herbicide.
The seizures earlier this week followed searches of three premises in Bangkok and Pathum Thani, with a total of 144,200 litres of glyphosate confiscated, DSI officials said on Saturday.
The searches were carried out following a tip-off that the weed-killer was falsely declared as 2,4-D dimethyl ammonium. The practice is in violation of customs and substance control laws.
Glyphosate is classified as a dangerous substance and its use is restricted.
Armed with a search warrant and accompanied by specialists from the Department of Agriculture, DSI officers searched two companies in Wang Thong Lang and Yannawa districts of Bangkok on Dec 19 and another company in Lam Luk Ka district of Pathum Thani.
They seized chemicals, with an estimated value of 17 million baht, have been taken to a Department of Agriculture facility in Chachoengsao.
The National Hazardous Substance Committee in 2019 decided to limit the use of glyphosate and to ban the agrochemicals paraquat and chlorpyrifos in response to rising public health concerns.
The committee had voted earlier to ban glyphosate but changed its stance following lobbying by Bayer and the US government. A ban would have meant that US grain grown using the chemical could not enter Thailand.
The current regulation allows for glyphosate to be used in Thailand but only on certain food crops. Farmers must obtain licences from the Department of Agriculture and undergo training in its use.