Pathumwan police were alerted at 3.30am to the death of Pongsakorn Prawit, 25, from the eight storey Srichai Mansion apartment on Soi Rong Muang 5.
Pongsakorn, from Surat Thani, was renting a room on the third floor.
Police said footage from security cameras showed that Pongsakorn left his room and walked upstairs to the rooftop. Some tenants saw him falling at about 2am. His sandals were left on the rooftop.