SEOUL, 17 May 2015 (AFP) - Holding a four-shot lead over playing partner Gareth Paddison from New Zealand as they approached the 18th, Moon seemed intent on snatching defeat from the jaws of victory as he holed out with a triple bogey seven.
But he still managed to win by two clear shots, signing for a one-over-par 73 to finish the OneAsia event on four-under-par 284.
"I really don't know what happened at the last," Moon said. "My worst hole all week but thankfully I had a good lead."
Paddison, who bogeyed the last three holes, closed with a 74 to finish joint second with compatriot Ryan Fox, Australian Jason Norris and South Korean Kim Do-Hoon.
Kim made a late charge, birdying five holes on the trot from the 12th, but also bogeyed the problematic 18th at the Namseoul Country Club.
Moon, 32, had started the day two behind leader Norris, who was bidding to become the first foreigner to win the title in a decade.
The pair were level-pegging with seven to play but Moon pulled ahead with a birdie on the 13th, while Norris double-bogeyed the 14th.
Prior to his victory, Moon's best professional showing was second place in last year's Korean PGA Championship.
"Unbelievable! I have waited a long time for this," Moon said.
Defending champion Park Jun-Won from South Korea closed with a 76 to finish in a tie for eighth.
Leading final-round scores (South Korean unless stated):
284 - Moon Kyong-Jun 71-66-74-73.
286 - Kim Do-Hoon 76-67-75-68, Ryan Fox (NZL) 73-73-68-72, Jason Norris (AUS) 68-69-72-77, Gareth Paddison (NZL) 69-73-70-74.
287 - Lee Tae-Hee 71-72-72-72.
288 - Kim Tae-Hoon 71-73-73-71.
289 - Kang Sung-Hoon 72-74-73-70, Steve Jeffress (AUS) 70-74-74-71, Kim Woo-Chan 70-74-73-72, Kim Jeong-Hyup 73-73-71-72, Park Jun-Won 69-75-69-76.