Yang, who became Asia's first major winner by claiming the PGA Championship last year, battled wind and rain to card a final round of 71 for a combined 15-under-par.
Welsh pair Stephen Dodd and Rhys Davies were in joint second two shots back, with Johan Edfors, Mikko Ilonen and Jamie Donaldson tied for fourth on 12 under.
Yang said he enjoyed the winning feeling, even if it was tinged with anxiety.
"It's a tremendous honor. But it's nerve-wracking too," said Yang. "I always get tense after I've won a tournament - maybe it's the thought of the speeches I have to make.
"But I have a great sense of accomplishment and a wonderful feeling." Yang had to work hard for the win thanks to the tough conditions, but his bogey at the 18th was his first in 50 holes.
"I knew the weather wasn't going to be co-operative," he said. "I knew low scores weren't going to be easy for anybody, and I knew I was going to have to work to save par from time to time. Luckily I was able to do that successfully." Yang birdied the second but could not get close enough to the pin to give himself many more opportunities. On the par four 11th he avoided a bogey despite making two visits to the sand, and had further sand saves on 13 and 15.
Yang finally put a little clear water between himself and the field with a birdie on the par-5 14th.
Davies, meanwhile, was pleased to continue his recent good form.
The Welshman won in Morocco in March, was third at the Malaysian Open and is in with a chance of making Europe's Ryder Cup team.
He made the cut on Friday with a stroke to spare but played the last 43 holes without a bogey on his card, shooting the lowest scores of the day on both Saturday (65) and Sunday (67).
"I'm especially pleased about that," he said.
"That's well over half of the competition. Unfortunately it took me a little while to adjust at the start of the week, there is grain on these greens and I struggled early on. But once I got the feel right I started to roll in some good putts."
