Choi was 3-under through the first two rounds and 1-under through seven holes Saturday before the strong charge set a course record and moved her to a 13-under 203. Lee had five birdies and a bogey in a 68 Saturday to also get to 13-under with one round to play.
Lydia Ko, with a third-round 79, is in third at 11-under and Suzann Pettersen, who was even-par 72 Saturday, is fourth at 10-under.
Second-round leader Caroline Hedwall battled through a round that included seven bogeys for a 2-over 74. She slipped into an eight-way tie for fifth at 9-under.
Lee posted birdies at 1 and 9 on the opening side Saturday and added a third birdie at the 12th hole. She had a bogey -- only her second of the week -- at No. 13 and pulled even with Choi with birdies at 15 and 16.
Choi opened with a birdie at No. 1 and then had six pars before an eagle at the par-5 eighth started her charge. She made the turn at 4-under after a birdie at the ninth hole.
The second nine opened with back-to-back pars and she had a birdie at 12 before her lone bogey of the day at 13. Choi ran off four straight birdies to jump up the leaderboard and pulled ahead with an eagle at 18.