The world No. 1 had 10 birdies and three bogeys to take a one-stroke advantage over Chella Choi, who capitalized on mild morning conditions at Sky 72 Golf Club to set the early pace at 6 under.
Tseng overcame a poor start, bogeying two of her first three holes.
“I felt a little off and my tempo was off in the beginning,” said Tseng. “I tried to figure out what to do with my swing.”
Once Tseng figured it out, the world No. 1 went on a torrid streak with birdies on seven of her next 11 holes.
After missing a 3-footer for par on number 16, Tseng reached the green in two on the par-5 18th hole for a birdie to reach 7 under par.
Tseng could not remember the last time she had 10 birdies in one round on tour. She could have gone even lower considering her three bogeys all came on three-putts.
The Taiwan native has already won five tournaments this year and is on pace to sweep the LPGA’s season-ending awards.
The winner of the inaugural 2002 edition of this tournament, Se Ri Pak, was off the mark with a 4-over 76.
After this week, the LPGA heads to Malaysia and Taiwan and then wraps up its Asia swing with the Mizuno Classic in Japan in early November.