Police from the Phibun Mangsahan police station entered the Suan Sawan Temple in Tambon Pho Sai on Wednesday morning following complaints from local residents that monks at the temple were taking drugs and disturbing the neighbourhood with loud noise.
Phra Apichai Wongkhoon, 27, tested positive for narcotics and was promptly defrocked.
Two men who voluntarily left the monkhood on Monday, but were staying at the temple with Apichai, also tested positive for drug use. They were also arrested.
The three were sent for mandatory rehabilitation.