Kims birdie at the long par-4 18th gave her a 71 for the day and a total score of 8-under-par 136 through 36 holes at the Magnolia Groves Golf Course.
She leads by a stroke over Se Ri Pak, who shot 67 Friday to end at 7-under, and by two over fellow South Korean Grace Park, who carded a 69 to be in solo third at 6-under.
Kim is searching for her fourth career victory on the LPGA Tour.
While her round on Day 2 was not quite as spectacular as her opening score of 65, she maintained well enough to stay out front.
Following a birdie at the par-5 4th, Kim struggled with bogies at Nos. 7 and 8, but rebounded with another birdie at the ninth.
She would go on to birdie the 15th and 18th, but another bogey managed to sandwich itself between them at the 17th.
Nevertheless, she ended the lowest of three very good and very young golfers of South Korean dissent.
Meanwhile, American Emilee Klein shot 69 on Friday to end in outright fourth at 5-under, while Meg Mallon (69) and Dottie Pepper (73) are four strokes off the pace at 4-under.
After a solid opening round of 69, defending champion Karrie Webb struggled on Friday, making five birdies, but also six bogies for a 74, which puts her at 1-under for the tournament.
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