The 26-year-old finished the final round with an even-par 72 for a tournament total of 18-under-par 270 in a close finish at the Pondok Indah Golf Course in Indonesian capital Jakarta.
For the Thai golfer nicknamed ‘Fever’, victory came after a poor first half of the season.
“I feel so happy about this win you know. The last few weeks I didn’t feel confidence like this,” he said.
“I didn’t think I was going to win this year to be honest, but I just planned to just keep doing my best.”
He secured a US$90,000 (B3.1 million) prize for his efforts on the Indonesian leg of the Asian Tour.
Nitithorn was trailed by Australia’s Scott Hend, England’s Steve Lewton and Taiwan’s Lee Chieh-po, who all carded four-under-par 68s in the final round to finish two shots behind overall.
Both Lewton and Lee missed late chances to snatch victory from Nitithorn.
“I just didn’t capitalise on a couple of the good shots I hit,” said Lewton.
Lee was more upbeat about his final round that pushed Nitithorn all the way.
“I am happy with the result. I didn’t think I had a chance when we went out today,” he said.
South Korea’s Yongjun Bae tied for fifth place after breaking the course record with a final round nine-under-par 63.
He tied with fellow countryman Mingyu Cho, Thailand’s Pavit Tangkomolprasert and Taiwan’s Chang Wei-lung.
The next leg of the Asian Tour is the International Series England in Newcastle, which begins on Aug 17.