The world number 62's final round one-over-par 72 proved enough to secure his fourth Asian Tour title on six-under 278 for the tournament at Woo Jeong Hills Country Club.
Jazz had started the day with a two-shot cushion and three birdies on a flawless front nine gave him a five-shot lead at one stage.
Calamity struck at the par-four 11th hole, though, when the 23-year-old found the water with an iron and three-putted on the green for a triple bogey seven that cut his lead to one stroke.
Hwang, up ahead, failed to capitalise, however, as he fluffed a short par-putt at the 13th but Jazz lost the extra shot again with a bogey after another three-putt on the 14th green.
The nerves increased for Jazz again at the 17th when, with Hwang having boomed a huge drive down the 18th fairway, the Thai left himself with a 15-foot putt for par.
Taking up the long putter that he adopted only two weeks ago, Jazz nailed the putt before parring the 18th with a tap-in to clinch the title.
"A national title is always a big thing so I'm really grateful and honoured to win this tournament," Jazz said.
"It's a very tough golf course, I got away with most of it but some of the holes coming in I was struggling. The pressure was on and after that seven, everything was harder."
Hwang, who finished with a 70, had the considerable consolation prize of a place at his first major championship at the age of 44 after securing one of two spots up for grabs at next month's 148th British Open at Royal Portrush.
With Jazz, who will move to the brink of the top 50 in the world with the victory, and third-placed American Chan Kim already qualified, South Korean Jang Dong-kyu, who shared fourth, claimed the other ticket to Northern Ireland.
(Reporting by Nick Mulvenney in Sydney, editing by Alan Baldwin)
