Choi had eight birdies and one bogey on the Highland Meadows course to take a one-shot lead over Alena Sharp.
Choi carded her lowest score since a 64 in the final round of the LPGA Tour Championship in November. She is a two-time winner on tour with both victories coming in 2009.
Choi credited a new putter with injecting new life in her game. She required just 22 putts over 18 holes to complete the round.
"I felt I needed to trust myself more," Choi said. "So I changed putters for good setup and trust."