Starting the final round four shots off the lead, Tanapat shot two eagles, four birdies against three bogeys to finish on 67 for a four-day total of 15-under 273.
Tanapat finished one stroke ahead of Teerawat Kaewsiribundit and third-round leader Suradit Yongcharoenchai, reports the Bangkok Post.
Tanapat, who became the only winner of multiple events on the tour this season, received B750,000 for his victory while Teerawat and Suradit pocketed B375,000 each.
“Winning this tournament for the third consecutive time is an amazing feeling,” said the 26-year-old.
“I would like to thank my parents and everyone who has been supporting me. To win the trophy at Santiburi really gives me a boost and I believe more good things will come.”
Traitanwa Thongsuk, 15, finished in 15th place and received the Supaporn Mapuenpong award for the best amateur player.
The 53rd Thailand Open, which is the final tournament of the season, will be held at Riverdale Golf Club, Pathum Thani, from Dec 4-7.