Winless in 73 LPGA Tour starts, Kim finished second in the LPGA Championship in late June, then lost a playoff to Choi the following week in the Jamie Farr Classic.
Choi also shot a 68 on Sky 72 Golf Club’s Ocean Course.
Vicky Hurst was third at 6 under after a 70.
Juli Inkster, the 50-year-old Hall of Famer who bogeyed the final hole last week in Malaysia to finish a stroke behind winner Jimin Kang, was three strokes back at 5 under after a 68. Inkster is trying to become the oldest LPGA Tour winner.
Second-ranked South Korean star Jiyai Shin was 3 under after a 68, and No. 1 Cristie Kerr was another stroke back after her second straight 71.
Michelle Wie shot a 73, leaving her 1 under.