Two Pakistani men were arrested after heroin and ketamine worth about 95 million baht were found hidden inside packets of powdered tea in their bags when they arrived at Suvarnabhumi airport.
Customs Department director-general Patchara Anuntasilpa and representatives of the Office of the Narcotics Control Board and the Narcotics Suppression Bureau announced the arrests on Tuesday.
The arrested men were aged aged 26 and 35 years. Their names were withheld.
They had travelled from Jinnah International Airport in Karachi via Dubai International Airport to Thailand on an Emirates flight that landed at Suvarnabumiu on Monday, Mr Patchara said.
When customs officers checked their bags they found 1.1 kilogrammes of heroin and 30.6kg of ketamine in packages of powdered tea, he said. The drugs were worth around 95 million baht.
The pair admitted to being paid 20,000 baht each by a Pakistani man to carry the luggage into Thailand, according to media reports. After they passed through customs, someone was to come and collect the bags.
Mr Patchara said the investigation was being extended to find the major players involved.