Nirat began the final round with a five-shot lead and the margin got as close as three on the back nine Sunday. That was the final cushion as Nirat finished at 22-under-par 266, three clear of Rafael Echenique at Yalong Bay Golf Club.
The win was Nirat's first and capped off an amazing week for the 23-year-old. On Thursday, he established a new course record at Yalong with an 11-under-par 61. One day later, he tied David Howell's 36-hole mark at 17-under-par 127, which was also tied the Asian Tour record for lowest opening 36-hole score.
While he was only 5 under par for the weekend, he avoided the fate of Howell. Last year, Howell was 17 under par through the first two rounds and ended up losing by five shots to Johan Edfors.
Instead, Nirat became the third Thai golfer to win on the European Tour after Thongchai Jaidee and Thaworn Wiratchant.
'There was a lot of pressure, but I talked to my caddie and the plan was to just keep playing at the same level as the first three days,' said Nirat, who gained a European Tour card for the remainder of the year.
Echenique shot a 4-under 68 on Sunday and was the only player to post four rounds in the 60s for the week. He finished alone in second place at 19-under-par 269.
Prayad Marksaeng carded a 5-under 67 and took third place at minus-17. Simon Nash shot a 4-under 68 and tied for fourth place with James Heath, who fashioned a round 3-under-par 69. The pair finished at 16-under-par 272.
During the final round, it would take several factors for Nirat to miss the winner's circle. With a five-shot lead, someone would have to go very low, coupled with some miscues from Nirat.
Neither really happened.
Nirat played steadily over the front nine with eight consecutive pars. He tallied his first birdie at the ninth, but dropped a shot at the par-4 10th.
After the bogey, things got a little tighter on the back nine.
Echenique became the main contender thanks to three birdies in his opening nine holes. He needed some additional birdies on his second nine as he was three back, but squandered some opportunities.
At both the 13th and 14th holes, Echenique had birdie looks from inside 6 feet, but missed both. He got up and down from off the green for a birdie at the par-5 16th, but that only closed the gap to three as Nirat collected his second birdie of the round at the par-3 15th when his 30-footer found the bottom of the cup.
Nirat parred his final three holes to secure the victory.
'I was feeling serious because on the back nine Rafael was getting close, so I didn't want to make mistakes,' acknowledged Nirat. 'At the finish I was very happy.'
Taichi Teshima, who shared second place at the start of the final round, struggled to a 1-over 73 and tied for sixth place with David Bransdon (66), Wen-Chong Liang (70) at 15-under-par 273.
European Ryder Cup stalwart Lee Westwood (70), Pelle Edberg (70), Australia's Peter Fowler (69) and Marc Warren (67) shared ninth place at 14-under-par 274.
Miles Tunnicliff, who was tied with Teshima for second place Saturday night, fared even worse than Teshima on Sunday. He shot a 3-over 75 and was part of a group in 13th at minus-13.