A total of 16 tonnes of the chemicals isosafrole and safrole, which are used as precursors to make ecstasy, were incinerated on Thursday in Samut Prakan province.
The Office of the Narcotics Control Board (ONCB) set fire to the seized chemicals, which could have produced more than 20 million ecstasy tablets, at the Bangpoo Industrial Estate.
The incineration process was presided over by Justice Minister Paiboon Koomchaya.
Permpong Chaovalit, secretary-general of the ONCB, said the Khlong Yai police station in Trat province had kept the chemicals in storage since 2008 to use as evidence against suspects in several cases.
But they can now be destroyed, and that way they will not be used in illegal activities, Mr Permpong said.
This is only the second time that caches of isosafrole and safrole have been incinerated in Thailand. In September 2010, around 50.4 tonnes of the chemicals — which would have produced more than 63 million ecstacy tablets — were burned, he said.
Gen Paiboon said the key to tackling drug trafficking efficiently is to stop it at the point of production.
More stringent measures must be taken to stop precursor chemicals from being transported to narcotics-producing countries, he said, adding Thailand is a major transit point for drug-trafficking rings in neighbouring countries.
The ONCB plans to call a meeting with precursor-producing countries in the region to exchange information about the drug trafficking situation in each country and boost joint efforts to crack down on precursor production.
Meanwhile, three drug suspects alleged to be members of the "Dew Kalasin" drug trafficking network were arrested in Udon Thani yesterday.
The suspects were identified as Attachai Phuden, 34, Sirisak Thippayarat, 19, and Thawatchai Payakchon, 22.
Police found on them 36 speed pills, 49,600 baht in cash, a 9mm pistol and fifty 9mm bullets, which have been impounded, officers said. Police also seized three of their vehicles including a Chevrolet, a BMW and a Honda.
Pol Col Nattakhet Hamkhamhai, deputy chief of Udon Thani provincial police, said officers received a tip-off about the drug gang.
Police then posed as clients to purchase illegal drugs and nabbed Mr Sirisak.
Mr Sirisak's statement led to the arrest of the two other suspects, Mr Attachai and Mr Thawatcha, who had recently been freed after serving jail terms for drug offences in Kalasin.
Mr Attachai allegedly told police he had obtained the speed pills from two men, Tuan and Bew, who he said were drug dealers in Laos.