Hise Chhiring Tamang, 42, originally from Kathmandu, flew from New Delhi in India to Kuala Lumpur, and then on to Phuket with Qatar Airways.
He admitted that he had been paid the equivalent of B75,000 by an unidentified dealer to carry a suitcase with the hashish hidden in its cover.
Had he not been arrested, he said, he was expecting a call from another unidentified man who would then come and collect the suitcase.
Chhiring told police he had no idea who was behind the smuggling; his job, he said, was just to deliver.
He confirmed he had been a real monk in a temple in Kathmandu for 12 years, and said this was the first time he had smuggled drugs.
However, police believe he had done so a number of times. They noted that immigration records showed him entering Thailand four times in the recent past, through Suvarnabhumi International Airport in Bangkok.
A customs officer at Phuket International Airport, Monthira Cherdchu, said that smugglers wearing clerical clothing was a new ruse employed by smugglers, who believed it was easier for them to get through Customs dressed as monks.
Chhiring will be sent to Tha Chatchai Police Station for further questioning.