Choi shot a final-round 3-under-par 68 for a 72-hole total of 15-under 269. Tseng had a 6-under 65 for the best round of the day Sunday but it wasn't enough to pass Choi. Tseng was second at 14-under 270.
Azahara Munoz shot 69 Sunday and took third, three strokes behind Choi. Pak Se-ri, who also had a final-round of 69, was fourth at 10-under 274.
Tseng, who was in fourth four strokes behind Choi after Saturday's play, was in the group ahead of Choi on Sunday and kept the pressure on throughout. She tied Choi several times over the final round but Choi answered with a birdie each time she needed to through 15 holes.
Tseng moved back in a tie with a birdie at 16 and Choi settled for a par. But on the par-3 17th, which Tseng parred, Choi dropped her tee shot within 5 feet and made the birdie putt. Both players had pars on 18 and Choi had her first championship of the year.