Organizers ended the $3 million tournament at 54 holes after the fourth round was abandoned at the par-71, 7,169-yard Serapong course at Sentosa Golf Club.
'I am very happy to defend a title for the first time,' Scott said. 'I had a real fight on my hands with Ernie. I got off to a fast start and he didn't. He played some spectacular shots out there.'
Before the final round was abandoned, Els and Scott had shared a three-stroke buffer on the leaderboard at 10-under after eight holes, with the South African making an eagle and two birdies but conceding two bogeys. Scott was mistake-free with two birdies.
'I hit a lot more fairways here than I normally do. I played a lot of good shots out there. My putting was good in spots,' Scott said.
The playoff was based on third-round scores, which Scott and three-time major winner Els led by three strokes at 8-under 205.
The playoff began with both making par on the first two holes.
On the third playoff hole -- the par-5 No. 18 -- Els drove the ball into the rough, but chipped back onto the fairway before guiding the ball to about 24 feet from the pin. His first putt placed the ball within 8 feet, but it was all over for the Big Easy when he missed his next attempt and bogeyed.
Scott teed off on No. 18 with a drive over water that found the fairway. He landed his second shot on the sloped and rough fringe of the green. A birdie putt from about six feet secured the Australian's win.
'In the playoff, I had my chances, man... It is disappointing,' said Els, who last appeared in Singapore in 2003 at the Singapore Masters, where he blew a lead to China's Zhang Lianwei on the final few holes.
Australia's Brad Kennedy finished in third place, one stroke ahead of China's Liang Wen-chong. India's Shiv Kapur was in fifth place, while Anthony Kang of the United States and Thailand's Prom Meesawat were a stroke back in a tie for sixth.
England's Lee Westwood was eight strokes off the pace with a three-round total of 213, while Shingo Katayama of Japan was a stroke behind.
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