'I'm really speechless,' admitted Wi, who played on the PGA Tour in 2005. 'Coming in here, I wasn't expecting to win. I just feel fortunate. I got a lot of good breaks today.'
Jaidee's bid for three consecutive victories came up short as he posted a final-round, 6-under 66. He completed 54 holes at 18-under-par 198.
The tournament was shortened to 54 holes because lightning storms plagued the tournament all week. A nearly three-hour delay on Thursday pushed the event back and Friday's action was suspended with half of the field needing to complete the second round.
On Saturday, the second round was finished, but after the final threesome completed their opening hole of the third round, lightning hit once again. Then, officials decided to trim the championship to 54 holes.
Raphael Jacquelin torched the Kuala Lumpur Club for a 10-under-par 62 on Sunday. He finished alone in third place at minus-17, followed by John Bickerton (66) and Mark Foster (63), who shared fourth place at 16-under-par 200.
Wi flew up the leaderboard on Sunday with a strong front nine that featured an eagle and three birdies. He tied for the lead with a birdie on the 10th hole, then matched Jacquelin in first at the time with a birdie at the 13th.
Wi took sole possession of first with a birdie at the 16th, then seemingly ran into trouble at No. 17. He pulled his 5-wood tee ball, but luckily hit a rock and bounced into the right rough. Wi knew he could not get to the green, so he laid up short. He was able to get up and down for par to stay at 18 under. The par was clutch considering Jaidee birdied 16 to match him at minus-18.
'I think that was the turning point,' admitted Wi. 'I was really proud that I was able to deal with that situation in such a calm manner. In the past, I would have just gone for it and get it near the green, but I told myself to stay patient and give myself a chance at par.'
Wi did not know Jaidee birdied 16 when he reached the par-5 18th. His third shot landed 5 feet from the hole and he converted the birdie putt to get in at 19 under par.
Jaidee had one chance left to make birdie, force a playoff and go for his third straight win here. He left himself 18 feet for birdie, but missed the putt and settled for second place.
'I don't think I denied him,' said Wi, referring to Jaidee. 'He's such a solid player. Even on the last putt, I thought he was going to make it and that I would go into a playoff. Luckily, it turned out my way.'
Jaidee looked well on the way to title No. 3 with four birdies in a five-hole span on the opening nine. He bogeyed the eighth, but birdies at 11 and 14 returned him to the hunt.
He birdied No. 16, but ultimately came up short.
Chinarat Phadungsil (66) and Gary Simpson (67) tied for sixth place at minus-14. David Park, who led after two rounds, struggled to an even-par 72 in the final round and shared eighth with Francesco Molinari (70), Graeme Storm (65) and Mattias Eliasson (66) at minus-13.
Padraig Harrington, playing in his first tournament of 2006, shot a final- round 67 on Sunday to finish in a group tied for 13th at 11-under-par 205.