Police went to Wat Pa Samakkhi at 12.30 am on Wednesday and found that the abbot, Phra Wiroon, 49, was not sleeping but sitting in his room.
Police tested his urine and found that it tested positive to drugs.
Pol Major Supicha Butrchiangkham, an inspector at the Bueng Kan police head office, said police had received complaints that the monk had acted improperly by abusing drugs, drinking alcohol and watching pornographic movies.
Police searched the room and found four bottles of white liquor. His mobile phone was found to contain a lot of pornographic videos.
The monk, whose lay name is Wiroon Rojanathamkul, admitted that he had taken a methamphetamine pill before police arrived.
He was defrocked and he voluntarily entered a drug rehabilitation programme run by the Lao Luang police station.