World No. 1 Yani Tseng, a winner in two of four starts this year, fired a four-under par 68 to seize a two-stroke lead after the second round of the $1.7 million LPGA Kia Classic.
Taiwan's Tseng, a favorite in next week's first major event of the year at Rancho Mirage, sank an 18-foot birdie putt on the 18th green to finish 36 holes on nine-under par 135, two strokes ahead of South Korean Se Ri Pak.
"I told myself (at the 18th tee) I just needed one good drive, one good shot and one good putt and I'm done for the day and that's what I did," Tseng said. "I just have to be patient, play my game. I should be all right this weekend."
A group sharing third place on 139 included England's Jodi Ewart, Sweden's Caroline Hedwall, American Alison Walshe and South Korean Jiyai Shin.
"I have two more rounds so it's plenty, just four strokes behind," Shin said. "I feel really good with my shots. I'm doing well with my putting, so I think two rounds is enough."
Tseng seeks her 15th career title and second in as many weeks. She has already defended a title in Thailand and captured the LPGA Founders Cup last week.
Last year, Tseng won 12 titles worldwide in a breakout season, seven of them in LPGA events and two at majors. She was second last year at Rancho Mirage to American Stacy Lewis.
Tseng birded the par-5 third and par-4 fourth and fifth holes on Friday but stumbled with back-to-back bogeys on the par-5 seventh and par-3 eighth.
She began the back nine by blasting out of a greenside bunker and into the cup for a birdie and added another birdie at the par-4 13th with a long putt from off the front of the green, setting up her closing birdie effort.
"I figure I could have shot lower," Tseng said. "I hit some bad shots but I hung in there and didn't give up and made a few more on the back nine.