Shin is at 13-under 131 after 36 holes of the 54-hole tournament. Stacy Lewis moved into contention with an 8-under 64 -- also bogey-free -- and is at 11-under while Yani Tseng (65 Saturday) and Miki Saiki (67) are tied for third at 10-under.
First-round co-leader Yukari Baba shot even-par 72 in the second round and is tied for seventh, six strokes off Shin's pace.
Shin had a pair of front-side birdies but took control with four more on the second nine. She beat par at 10 and 13 to take the outright lead and added birdies at 16 and 18.
"I didn't make any bogeys and made six birdies. My shots were really good," Shin said. "Usually when I play as the leader, I try to not make mistakes but I think tomorrow I have to be aggressive."
Lewis was 4-under after six holes and closed with four more birdies in her final six holes.