Yang, who finished eighth at the Masters Tournament last week, had briefly doubled his overnight advantage to two shots at 15 under par after posting an early gain at the second, but could only manage seven consecutive pars after unusually missing several birdie putts on the wetland style front nine.
Welshman Jamie Donaldson, who began the final day a shot adrift of Yang alongside Mikko Ilonen, battled back from an early dropped shot with back-to-back birdies to sit alone in second with compatriot Rhys Davies charging into contention just two adrift on a damp final day at Jinji Lake International Golf Club.
After winning his maiden European Tour title in Morocco last month, Davies played the opening 11 holes of his final round in five under par with the 21 year old Challenge Tour graduate bogey-free and 12 under par for 29 holes over the weekend after a third round 65.
Another Welshman in former champion Stephen Dodd improved to 12 under par through ten alongside Ilonen - the Finn one over playing in the final group alongside Yang after a par putt at eight agonisingly lipped out.
With a persistent light rain hitting the course just as the leaders began their final rounds, Yang quickly doubled his overnight lead after his brave decision to take on the par five second - the longest hole on the course at 615 yards - paid dividends.
The Korean did find the bunker at the back of the green after ensuring he cleared the creek 50 yards short of the putting surface, but expertly chipped up to two feet to complete the up and down with a simple putt for birdie for a second consecutive day.
Donaldson fell three off the pace after a four foot par putt at the fourth lipped, but quickly rejoined Ilonen two adrift as he made a similar short range putt but dropped a hole later with Davies, Johan Edfors joining Pablo Larrazabal at 11 under.
A rare missed putt from the usually reliable Yang from four feet at the short par four fifth allowed Donaldson to cut the Korean's lead to a single shot with a 15 foot putt at the par three sixth handing the Welshman back-to-back birdies.
Yang had chances at the sixth and seventh to extend his lead but an eight foot effort at the seventh rolled just past the edge before Donaldson rolled a 20 foot birdie putt at inch past the hole at the tenth.