The body of the man, aged 48, was found in the laundry of the establishment about 2.30am on Thursday. Police believe he could have been dead for up to five hours.
The owner of the guesthouse off Phrabaramee Road, Boonsom Manutnoi, 55, said the man was constantly drunk.
Police believe there are no suspicious circumstances. The man's body has been taken to Patong Hospital.