Thaworn, who started the day with a three-stroke lead, carded a safe 2-under 70 for an aggregate of 16-under 272 to finish two strokes ahead of Indian veteran Gaurav Ghei.
It was the third title of the year for Thaworn, the Asian Tour Order of Merit leader.
Ghei, tied eighth after the third round, carded the day's best score of a 6-under 66 to take the second spot, a stroke ahead of Thailand's Prom Meesawat and South Africa's Hendrik Buhrmann.
Thaworn, 39, later said the course did not suit his game, and that the victory came as a surprise.
'At the beginning of the week, I did not believe I could win the tournament,' he said. 'I've missed cuts here on this course. Fortunately, I did not lose a ball this week.'
Thaworn, who led the field after the second and third rounds, dropped two shots on the front nine but made two birdies as well, and another two on the back nine.
Ghei could have put more pressure on the Thai golfer but missed three birdie chances on the 14th, 15th and 16th holes, when the ball went painfully close to the hole but did not fall in.
'After that miss on the 14th, I knew that my chances were slim, because Thaworn was not going to give it away from there on,' said Ghei.
India's Jyoti Randhawa, fourth after the third round, scored a 1-over 73 to tie for sixth spot with compatriot Mukesh Kumar, who closed with a 68.
PGA Tour player Arjun Atwal, a pre-tournament favorite, finished with a 70 to tie for the 11th spot with three others.
Copyright 2005 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.