Kim capped her round at Wilshire Country Club with an unlikely birdie at the 18th to finish the day a stroke clear of Sweden's Maja Stark, Thailand's Chanettee Wannasaen and South Korean Kim Sei-young.
"Well, I chunked my tee shot on the last hole 20 meters short and then I chipped it in," Kim said. "I think that's pretty cool, in front of everyone."
Otherwise, Kim said, it was a straightforward day with plenty of birdie opportunities.
"I think I hit a lot of fairways, maybe missed one or two fairways, and then the shots I hit close, there were probably a handful so a lot of good birdie opportunities today," she said.
Stark also played without a bogey, picking up four strokes on the front nine before making two more birdies coming in -- all despite the fatigue lingering in the wake of her runner-up finish to world number one Nelly Korda at the Chevron Championship near Houston on Sunday.
"I was so tired when I got here," Stark said. "I've barely been practicing, just did a little bit of what I needed to do."
Korda, whose victory in the first women's major of the year was her fifth in five starts -- equalling an LPGA record -- withdrew from this week's event on Monday saying she needed some rest in preparation for the rest of the season.
Grace Kim, who won the Lotte Championship in Hawaii last year, missed the cut at the Chevron but said a fresh approach had helped her on Thursday.
"If I was to compare my round today to last week, I really focused on just not having too much in my mind," she said. "I think I over-thought a lot of things through my first and second round last week and struggled a little bit mentally."
Chanettee claimed her share of second on 65 with a round that included seven birdies before her lone bogey of the day at the 16th.
Kim Sei-young, who won the most recent of her 12 LPGA titles in 2020, teed off late and charged up the leaderboard with four of her six birdies in a four-hole span from the 12th through the 15th.
American Auston Kim, South Korean Ryu Hae-ran and Russian Nataliya Guseva were two shots off the lead on 66 with defending champion Hannah Green of Australia a further stroke back alongside Bianca Pagdanganan of the Philippines and South Korean Amy Yang.
