The South Koreans were among only six teams who broke par on Saturday (Sunday AEST), posting a 1-under 69 in foursomes to build their advantage.
After a terrific start to the tournament, double major winner Nelly Korda and Olivia Cowan made only one birdie, had a bogey on both par 5s at Midland Country Club and shot 76 to fall six shots behind.
Korda and Cowan were tied for 13th. It will be only the second time this year on the LPGA that Korda is not in the final group.
Kim and Choi, the South Korean duo who are both among the top 20 in the women's world ranking, were at 10-under 200.
"The wind was obviously very strong today so that was a big factor that was different than the first round," Kim said.Â
They also shot 69 in foursomes in the opening round.
Hira Naveed is the best-placed Australian and is in a tie for seventh with her American partner Gurleen Kaur.
Gina Kim and LPGA rookie Yana Wilson managed a birdie on the par-3 closing hole, which was playing downwind to a front pin over the water. That gave them a 70 and left them one shot back.
Alison Lee and Lilia Vu, former college teammates at UCLA, had the lead until they made a triple bogey on the 16th hole when Vu hit the tee shot out-of-bounds. They had to settle for a 69 and were in third place at 8-under 202.
"It's a pretty meaty hole. I've been kind of leaking my drives out right so just wanted to make sure I had a draw but it was a pulled draw instead," Vu said.
Juli Inkster, who at 66 became the oldest player in LPGA history to make the cut in an official event, teamed with Angel Yin for a 70. They were tied for 20th.
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