Thais are suspected of involvement in the smuggling of 3.9 tonnes of the methamphetamine precursor ephedrine from the Golden Triangle to Australia last month, according to the Office of the Narcotics Control Board (ONCB).
Information from Australia was that the liquid ephedrine seized in Sydney had originated in the Golden Triangle area in a country neighbouring Thailand and been transported by sea from Thailand to Australia, ONCB secretary-general Sirinya Sitdhichai said on Tuesday.
The Thai suspects were drug producers and dealers in the Golden Triangle, he said.
The ephedrine was found in bottles labelled as a popular brand of tea sold in most convenience stores.
It could not be confirmed at this time if it would have been used to illegally produce methamphetamine in Australia, according to Mr Sirinya.
However, it was the biggest haul of ephedrine ever seized in Australia, and enough for the production of three tonnes of crystal methamphetamine, or "ice", reportedly worth about 87 billion baht on the black market.
It was the second recent significant seizure of the precursor chemical in Australia. About four months ago, 1.4 tonnes of smuggled ephedrine was seized.
Methamphetamine abuse has become a major problem in Australia.