The 19-year-old, who hails from Melaka, crossed the finish line in 10.38s, beating defending champion Eric Cray of the Philippines who had to be satisfied with silver after clocking 10.43s.
Thailand’s Kritsada Namsuwun, who also clocked 10.43s, had to settle for the bronze based on the photo-finish while Khairul Hafiz’s teammate Jonathan Nyepa from Sarawak finished in fifth place in 10.66s.
However, Khairul Hafiz, who holds the national record of 10.18s, was far off the Games record of 10.17s set by Suryo Agung Wibobo (10.17s) of Indonesia at the Laos Games in 2009.
Khairul Hafiz, dubbed “Speedy Jantan”, had done better in the semifinals where he clocked 10.34s while Jonathan did 10.60s.
He will next be in action in the 200m tomorrow.
Meanwhile, in the women’s 100m final, national sprinter Zaidatul Husniah Zulkifli won the silver after clocking 11.74s.
The gold was won by Le Tu Chinh of Vietnam (11.56s) while Singapore’s Shanti Pereira took the bronze (11.76s).
Another national sprinter, Siti Fatimah Mohamad, finished in fifth place after posting 11.85s.