The 32 year old held off the challenge of Thailand's Namchok Tantipokhakul and Australian Michael Wright to take victory after carding a three under par 69 at Burapha Golf Club.
Liang arrived at the tournament in good form, having secured a top-ten finish at the US PGA Championship two weeks ago.
He started the final round with a one shot lead but found birdies difficult to come by and spent much of the day tied for the lead.
However, European Tour Member Liang holed a crucial 30 foot putt for birdie on the 16th to move clear of the chasing pack.
"I am very excited and I really enjoyed this tournament. It was close all the way as there were some very good players trying to win," he said.
"I was very tired when I arrived as my schedule has been hectic. So I wasn't very sure how this week would go. It gives me a lot of confidence to know I can play at this level after such a busy stretch."
The win moves Liang to the top of the OneAsia Order of Merit.