He recovered with an eagle on the par-five fourth and another birdie on the fifth for the day's lowest score at Sentosa Golf Club's Seropang course.
Philippines' Miguel Tabuena and Japanese duo Yuta Ikeda and Yoshinori Fujimoto were tied in second, one stroke behind Hung, who acknowledged he had benefited from the rub of the green and hoped his luck would continue.
"A lot of shots I didn't hit good but still managed to get in good positions," Hung said. "I have been here a lot of times, I know how challenging it is and I have not shot such a good score here before."
Defending champion Sergio Garcia overcame a bout of illness to end with a two-under 69 after a mixed round of four birdies and two bogeys, three shots off the lead.
"I've had a little bit of a sinus infection these last couple of days, and a bit of an upset stomach this morning," Garcia said. "But I think I played nicely."
An afternoon delay caused by rain and lightning kept half the 156-man field from finishing, with play suspended at 1910 local time. They will resume play at 0730 on Friday before the second round gets underway at 0940.
(Reporting by Rohith Nair in Bengaluru, editing by Larry King)
