CARLSBAD, 27 Mar 2015 (AFP) - Lee, who missed the course record at Aviara Golf Club by one stroke, birdied all four of the par-five holes, taking the lead with an eight-foot birdie putt at her 14th hole of the day -- the par-five fifth and adding one more birdie at the eighth.
"My long game didn't feel good, my swing didn't feel good, but I made a lot of putts," said Lee, winner of two LPGA titles last year who had a one-stroke lead over former world number one Tseng Ya-ni of Taiwan.
Lee said she'd practiced "a lot" since struggling to a 77th-place finish in Phoenix last week.
"I changed the grip," she said.
Tseng, chasing her first LPGA victory since a 2012 win in nearby La Costa, capped her 66 with a four-foot birdie at 18.
She gave herself the chance with an awkward shot from near a fairway bunker, standing in the sand and choking up on her seven-iron.
"I never thought I'd be that close," Tseng said of the shot that bounced and rolled toward the cup.
Tseng said she had a brief moment of worry that she might find the water to the right of the green.
"I was like 'Oh, if I hit it in the water I just go drop another ball. I've got a few birdies in my pocket and should be OK,'" said Tseng, whose round also included a 20-foot eagle putt from the fringe at the 10th.
Current world number one Lydia Ko, the New Zealand 17-year-old who caused a sensation when she reached the summit of the rankings in February, was among a group of four players sharing third on five-under 67.
She was joined by Australian Hall of Famer Karrie Webb, American Cristie Kerr and China's Lin Xiyu.
Ko has two victories worldwide this year, winning the Women's Australian Open and the New Zealand Open in back-to-back weeks.
She has 10 straight top-10 finishes and has broken par in her last 25 LPGA Tour rounds, and is warming up this week for a bid for a first major title at next week's ANA Inspiration, formerly the Kraft Nabisco Championship, in Rancho Mirage.
"It's not easy," Ko said. "I'm trying to take one round at a time, one shot at a time... Playing weeks back to back and all courses just being different, I think that's the hard thing. But I'm just trying to keep focused."
Former world number ones Park In-Bee and Stacy Lewis, now ranked second and third in the world, led a group of 10 players on four-under 68 that included fourth-ranked Kim Hyo-Joo -- who won her second LPGA title in Phoenix on Sunday.
Leading first-round scores on Thursday in the LPGA Tour Kia Classic (USA unless noted, par-72)
65 - Lee Mi-Rim (KOR)
66 - Tseng Ya-ni (TPE)
67 - Cristie Kerr, Karrie Webb (AUS), Lin Xiyu (CHN), Lydia Ko (NZL)
68 - Laura Diaz, Karine Icher (FRA), Park In-Bee (KOR), Brittany Lang, Stacy Lewis, Lexi Thompson, Jackie Stoelting, Austin Ernst, Kim Hyo-Joo (KOR), Chun In-Gee (KOR)
69 - Pak Se-Ri (KOR), Jenny Rosales (PHI), Michelle Wie, Paula Creamer, Alena Sharp (CAN), Jane Rah, Sakura Yokomine (JPN), Thidapa Suwannapura (THA), Beatriz Recari (ESP), Moriya Jutanugarn (THA), Alison Lee, Brooke Pancake