Wiratchant completed the event with a score of 25-under-par 255 to become the second native of Thailand to win an event on the European Tour's International schedule.
His total of 255 was the lowest aggregate score in European Tour history, though preferred lies rules were in play.
Raphael Jacquelin posted a 5-under 65 in the final round to take second place at 20-under-par 260. Adam Fraser, who aced the par-3 17th in the final round, posted one of the six rounds of 8-under 62 shot during the tournament to finish alone in third place at 19-under-par 261.
Colin Montgomerie, who likely needed to win the event to return to the top 50 in the world rankings and gain entry into The Masters, fired a 10-under 60 in the final round to climb into a tie for fourth place at minus-18. He was joined there by Frankie Minoza, who closed with a 4-under 66.
The tournament was able to finish on schedule as both the third and fourth rounds were completed on Sunday after there were weather delays each of the first three days.
Wiratchant carded three birdies in the final nine holes of his third round Sunday before starting his final round with a three-stroke lead at minus-18.
The Thailand native was starting to feel pressure from other players early in the final round, but regained full control of the event as he converted back- to-back birdie putts from the par-3 fourth at Cengkareng Golf Club.
Wiratchant moved to 21 under when he birdied the par-5 ninth. He continued his hot play around the turn as he drained another birdie putt on No. 10. Wiratchant completed a run of three straight birdies as his birdie putt at the 11th found the bottom of the cup.
He converted a birdie putt at the par-4 13th to climb to 24 under. Wiratchant tripped to just his second bogey of the tournament at the par-4 14th. Both his bogies during the tournament came on No. 14.
Wiratchant came right back with a birdie on 15 and closed with a birdie at the last to finish at 25 under for his first win on the European Tour.
'Winning a co-sanctioned event has been on my mind,' said Wiratchant, who joined Thongchai Jaidee as the two Thai winners on the European Tour. 'I've been trying for a while and my dream has now become a reality. The weather disruptions earlier this week made it hard for us, but I just tried to ignore them.'
Jacquelin, who played two groups ahead of Wiratchant, put some early pressure on the eventual champion as he birdied three of his first six holes. Jacquelin birdied the ninth for the fourth straight round to move to 19 under. He only managed one more birdie on the way in however.
Montgomerie began the final round 10 strokes behind Wiratchant. He parred the first five holes of his final round as he started on the 10th tee. The Scotsman moved to 9 under with a birdie on the par-4 15th.
The seven-time Ryder Cup performer then went on a run that put him into the European Tour record books.
Montgomerie birdied 17 and 18 to make the turn at 11 under. He then birdied the first seven holes of the front nine to become the first player in European Tour history to birdie nine consecutive holes. However, he could only par the eighth and ninth, where he missed a 10-foot birdie putt, to post a 60.
'I had a golden opportunity,' said Montgomerie of his chance to break 60. 'I hit my sand wedge in there to about 10 feet, but the grain grabbed the ball and it didn't really roll the way the other putts had. I don't know what I took on the 15th tee, but I want more of it.'
Japan's Eiji Mizoguchi posted a 4-under 66 in the final round to finish alone in sixth place at 17-under-par 263. Chris Williams, Marcus Both, Ariel Canete and Gary Simpson finished one stroke further back at minus-15.