Lee, whose only blemish this week is a double-bogey 5 at the 11th hole Friday, moved to 10-under 134 after 36 holes. Rikako Morita, who closed with three bogeys in her final four holes for a 68, is second at 6-under 138 for the tournament.
First-round co-leader Ayako Uehara was even-par 72 Saturday and is in a five-way tie for third at 4-under for the tournament. Jenny Shin and Karine Icher each shot 3-under 69 while Choi Ne-yeon and Angela Stanford both had 71s in the second round in joining Uehara in third.
Jayai Shin, who was tied with Uehara for the lead after Friday's first round, turned in a 1-over 73 Saturday and is tied for eighth at 3-under. World No. 1 Yani Tseng is also in that eight-player group.
Lee opened the second round with a birdie at the first and, after four pars, posted three birdies in the next four holes for a first nine of 4-under. She quickly got to 6-under with birdies at 10 and 11 -- the par-3 she had a double bogey on Friday -- and moved further ahead with birdies at Nos. 14 and 15.