The 2015 champion closed with a four-under 68 at the Siam Country Club in Chonburi to finish with a 22-under-par total of 266, one shot lower than the previous record and well clear of nearest rival, fellow Korean Ryu So-yeon (68).
Compatriot Kim Sei-young finished a further two strokes back in third place, while Americans Lexi Thompson and Danielle Kang shared fourth place alongside another Korean, Chun In-gee, on 13-under-par at the rain-hit event.
Frustrating weather delays during the first three rounds left the players either battling boredom or needing to play almost 36 holes in a day, but Yang stayed focused throughout to claim a third LPGA title after leading for all four days.
"I'm beyond happy," Yang said in a greenside interview.
"It wasn't easy with all the rain delays, 4 a.m. wake-up calls two days in a row, but I stayed patient out there and did my best and am delighted to have won the tournament."
Starting her final round with a five-shot cushion, Yang always appeared in control of her destiny but when Ryu threatened to cut her lead to just two strokes on the back-nine, the 27-year-old produced a pair of title-winning shots.
Yang made a complete mess of her chip from beside the green on the par-four 14th but breathed a huge sigh of relief when she drained a difficult 20-foot downhill putt to match Ryu's par and keep her advantage at a manageable three shots.
"The chip wasn't easy from the bottom (of the slope) and I had a poor bounce but I knew I had to make the putt and fortunately I did," added Yang, who only recorded two bogeys all week.
Still pumped by the adrenaline of her clutch par-save, Yang sent a booming drive into the centre of the green on the short par-four 15th and was able to extend her lead by another shot with a tap-in birdie as Ryu's challenge faded with a par.
"I love this place, I love the people here and I always seem to play well," Yang said. "It's a great start to the year and I am really looking forward to the rest of the season."
(Reporting by John O'Brien in Singapore; Editing by Toby Davis)
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