Choi, despite a pair of second-nine bogeys, turned in a 4-under-par 67 in the second round for a 36-hole total of 10-under 132. She is two strokes ahead of LPGA rookie Sydnee Michaels, who had five consecutive birdies in one stretch en route to a 6-under 65 and two-round total of 134.
Suzann Petersen turned in the score of the day with a bogey-free 7-under 64 and is tied with Mika Miyazato (69) , Lizette Salas (67) and Momoko Ueda (67) for third place at 7-under. Karrie Webb, who was tied with Choi for the first-round lead, was even-par 71 in the second round and is among a group of five tied for seventh four strokes behind Choi.
Choi had three birdies in her first six holes and made the turn at 3-under. She opened the second nine with another birdie but had her first bogey of the tournament at No. 11. She posted back-to-back birdies at 12 and 13. A bogey at the 17th left Choi at 4-under for the day.