Pol Lt-Colonel Nopparat Muenwong, an inspector at Bang Khun Thine police station, said the body was spotted on Bang Khun Thien canal at the pier of Wat Nang Ratcha Worahan in Bang Khor sub-district of Jom Thong district at 8am.
The man wore a black t-shirt and black shorts. No identification documents were found.
His throat appeared to have a big cut and the right side of his head had a big wound.
The body was sent to Siriraj Hospital for an autopsy.