Seoul, Sept 9, 2012 (AFP) - The 29-year-old led by two overnight but held his nerve in a topsy-turvy final round for an even-par 72 to give him a nine-under total of 278 and the winner's cheque of around $178,000.
Kang Kyung-nam, who shot 68, and Park Sang-Hyun, on 71, both from South Korea, pushed Griffin all the way, to finish joint second on 279.
Kim Bi-o, winner of two events on the OneAsia circuit already this year, was a shot further back. His hopes of an unprecedented third OneAsia title on home soil came unstuck with two wayward shots on the par five 13th, although he salvaged a bogey with a breathtaking 60-foot putt.
"I am really, really thrilled," Griffin said after his victory. "This is what I have worked for all my life, so it is absolutely amazing to finally get there.
"This is immense. It gives me a lot of security and it also repays the faith that my supporters and sponsors have shown in me over the years."
Griffin, once ranked the third-best amateur in the world, was a relative latecomer to the professional ranks and only scored his first four-round victory at the South Pacific Open in New Caledonia last year.
He is a natural left-hander who plays the game right-handed. He dedicated his victory to Peter Beck, a friend and mentor who caddied for him occasionally in his amateur and professional days, who died in 2010.
Park was left ruing his missed opportunity, saying: "Very disappointed, that's the only thing I feel right now. I sort of think that somehow I was meant to be second in this tournament."
Final scores after round four of the 2012 High1 Resort Open, played at the par 72, 6,542-metre (7,148-yard) High1 Resort Country Club:
278 - Matthew Griffin (AUS) 67-70-69-72
279 - Kang Kyung-nam (KOR) 74-70-67-68, Park Sang-hyun (KOR) 69-71-68-71
280 - Choi Ho-sung (KOR) 71-68-71-70, Kim Bi-o (KOR) 72-70-67-71
281 - Garrett Sapp (USA) 74-72-70-65, Park Jae-kyung (KOR) 72-71-71-67, Aaron Townsend (AUS) 70-69-70-72
283 - Gareth Paddison (NZL) 75-70-70-68
284 - Lucas Lee (BRA) 72-72-70-70, Son Joon-eob (KOR) 72-72-70-70, David McKenzie (AUS) 70-73-70-71, Lee Jun-seok (KOR) 70-67-73-74