Pak has not won on the LPGA circuit in two years and has not had a top-10 finish this season in nine starts.
She birdied three of the last four holes at the Panther Creek Country Club to tie Lee, who became a professional five years ago.
Kris Tamulis was alone in third at 67, but only five shots separated the top 70 players.
Natalie Gulbis, Suzann Pettersen and Anja Monke were all at 68, while the large group at 69 included Paula Creamer, Cristie Kerr, Yani Tseng, Morgan Pressel and Laura Davies.
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