A Taiwanese man was found dead at his rented townhouse in Chon Buri province on Tuesday.
Police found traces of burning charcoal that suggested the 47-year-old foreigner might have committed suicide.
His body was lying on his bed, with a charcoal stove, a pan and some ashes at the end of the bed. A hand-written message that began with "I am sorry…" was also found.
Police broke into his home after being informed by his neighbours that he had not stepped out of his locked home for several days and a bad smell came from his house.
Police said the foreigner used to have a roommate, who, according to neighbours, had recently moved out.
The body of the deceased will be sent to the Institute of Forensic Medicine for an autopsy.