The bodies of Charlie Milsom, 35, a British citizen, and Jonathan Louis, 40, from the United States, were found in Louis' apartment Saturday morning, the Bangkok Post reported.
Louis' wife said she returned home from work Friday to find the men apparently dozing in the living room and discovered the next morning both were dead.
Thamaporn Apison said her husband had been taking medication for gout and more recently sleeping pills because of stress.
Investigators said they found prescription medication with Milsom's name on the bottle and four bottles of what was described as medication for drug treatment. They said autopsies were scheduled.
Apison said her husband and Milsom, who both taught English in Bangkok, were friends.