The arrest followed a sting operation at a hotel in Baan Kai district where police found Kiadtikun Panwongsa, 24, and seized a small package containing 7.68 grammes of marijuana.
Investigators said the man refused to co-operate in the interrogation and asked to be taken to jail. Officers then had him x-rayed and discovered 21 packages of crystal meth and five packages of dried marijuana.
Police were able to recover one package of crystal meth so far.
The man confessed to police that he had been paid 150,000 baht by a transsexual named Aon to deliver the merchandise to a prison inmate.