Ormsby carded a final round of 68 at Fanling to finish 11 under par, a shot ahead of Spain's Rafa Cabrera Bello, Sweden's Alexander Bjork and the American pair of Julian Suri and Paul Peterson.
The tournament looked to be heading to a play-off when Ormsby three-putted the 18th to leave Cabrera Bello needing to par the same hole to force extra holes.
However, Cabrera Bello then found the greenside bunker with his approach and failed to get up and down, leaving world-number-319 Ormsby to claim the second win of his professional career.
“It's been a great week again. I came from playing great last year, I finished second here. I felt that I give myself a really good chance coming in today again. I've been battling till the last hole. There's not really much more that you can ask yourself as a player than to have a chance coming up the last. The coin just didn't fall my side this time,” said Cabrera Bello.