TAIPEI, September 15, 2013 (AFP) - Thaworn, whose best result before this week was tied 28th in May, achieved a four-under-par 68 for a 13-under-par total of 275 in the $500,000 event.
Overnight leader Chan Kim of the United States led for most of the round, but stumbled in the closing stretch when he made three straight bogeys from the 15th hole.
He ended second after shooting a 70 at the Linkou International Golf and Country Club.
Angelo Que of the Philippines, a three-times Asian Tour winner, ended the event with a 66, the day's best round, to finish third on 279.
"I'm very proud because I can still win at the age of 46. I was really struggling with my irons but I chipped and putted so well. I honestly didn't think that I could win," said Thaworn, in comments supplied by the organisers.
He had traded two birdies and one bogey after four holes to trail Kim by three shots, but recovered after a one-hour suspension due to rain with a pair of birdies on five and six.
Thaworn added another birdie on 13 to secure victory as Kim faded.
"Kim is such a powerful golfer and he had a lot of advantage on the par fives. I had to stay patient. I didn't think I could have won and I would have been satisfied with second place. But he started to drop shots and all of a sudden I was in the lead and I won," said Thaworn.
Kim was upset at his late fade after starting strongly. He eagled the first hole from three feet and added birdies on holes three, four and 10.
"I got a little greedy. I tried to get my ball out further so I could get a shorter club into the green," the 23-year-old said.
"I think that's something which I have to learn, because all I had to do today was actually play a bit smarter. I will use this experience in my future tournaments."
Final scores Sunday in the $500,000 Yeangder Tournament Players' Championship at Linkou:
275 - Thaworn Wiratchant (THA) 69-67-71-68
276 - Chan Kim (USA) 70-68-68-70
279 - Angelo Que (PHI) 74-72-67-66
280 - Chan Shih-chang (TPE) 71-71-71-67
281 - Lu Chien-soon (TPE) 72-72-68-69, Chiragh Kumar (IND) 68-69-74-70, Baek Seuk-Hyun (KOR) 73-69-69-70, Hsu Mong-nan (TPE) 69-68-71-73, Yeh Wei-tze (TPE) 73-67-67-74
282 - Matthew Stieger (AUS) 69-73-72-68, Berry Henson (USA) 71-70-71-70