Tseng had seven birdies and a bogey in her final round at the Siam Country Club and finished at 15-under 273. Michelle Wie, who had a 2-under 70 Sunday, was second at 10-under.
The Thailand event was the first tournament on the 2011 LPGA schedule but Tseng had already won the Taifong Ladies Open in January in Taiwan and the Women's Australian Open and the ANZ Ladies Masters in Australia earlier this month. The Masters win pushed her to the world women's golf No. 1 ranking.
Wie and second-round leader Kim In-kyung kept close to Tseng through the front nine Sunday before Tseng posted three birdies over the span of holes 10-13 and pulled away.
Wie's Sunday's round included three birdies in the first seven holes but she was 1-over the rest of the way.
Kim was in contention at 5-under on the day through 13 but she staggered through a 9 on the par-4 17th hole. A birdie on the 18th hole allowed her to finish in a tie for third with Karrie Webb, whose 3-under 69 was remarkable after she had four straight bogeys from 2-5.