Three strokes behind leader Witchayanon Chothirunrungrueng after three rounds, Pawin closed with a final 67 to win on 11-under 269 at the par-70 Laguna Golf Phuket.
Witchayanon finished second with a 10-under aggregate after posting a 71 in the final round.
One stroke further back were Atiruj Winaicharoenchai (64) and Panuphol Pittayarat (70), who shared third on nine under at the two-million-baht final event of the All Thailand Golf Tour 2020.
Pawin received B300,000 and five world ranking points for his third tour win after victories at the Singha Championship 2018 and the Hua Hin Open 2015. Witchayanon, who is still waiting for his first ATGT title, took home B190,000 and three points.
Pawin, who turned pro in 2011, said he was able to win by staying focused on his own game.
“I have tried to concentrate on my own game and that helped a lot,” said the Suphaburi native, who had five birdies and two bogeys yesterday.
“My iron play was a lot better this week. On the back nine, I tried to play safe as much as I could.”
Kosuke Hamamoto finished sixth on eight under followed by Natipong Srithong (70), who was one shot behind.
Ratchapol Jantavara, who was bidding for back-to-back titles after his win in Chiang Rai last month, was joint-33rd on 281.
Amateur Ratchanon Chantananuwat, 13, finished as low amateur.
In his third ATGT event, Ratchanon, who was among four amateurs who made the cut, shot a final 67 to tie for 17th with a total score of a three-under 277.
In August, Ratchanon made the cut at the Pattaya Open, becoming the youngest player to reach the weekend rounds in the 21-year history of the tour.
Pavit Tangkamolprasert, who won the season-opening Boonchu Ruangkit Championship in January, finished tied for 63rd on 10-over 290, which was enough to earn him the Order of Merit champion’s crown with total earnings of B879,754 in six events.