In 2012, the Korean missed a putt from a foot to secure her first major title here at Mission Hills Country Club, and then lost the subsequent play-off to Sun-Young Yoo.
The 30-year-old has not been in contention in this tournament since then, but soared clear of the field on Friday with a superb round on a warm, windy day in California.
At eight under she leads by three shots from New Zealand’s Katherine Kirk, who signed for a 68, with American Ally McDonald (72) and Korean Jin Young Ko (71) at four under. Five players including home favourite Lexi Thompson (72) and England’s Charley Hull (69) are tied fifth at three under.
“I wasn’t really paying attention to the leaderboard because I’m just blessed to be here,” said Kim, who claimed her first major title at the 2017 Women’s British Open. “For a long time it was one of my goals (to win), but now I’m just really happy to be out here.
“I was seeing some lines today and getting my putting speed right. I knew my game has been getting better since last week. This morning was a little calmer and wasn’t very cold. The ball was actually flying a little shorter than yesterday, so I had to adjust that for a few holes in the morning.”
Kirk was six under for the day through 16 holes, but dropped shots on 17 and 18 to blight her scorecard.
“There were lots of positives,” said the three-time LPGA Tour winner. “The first 16 holes were pretty textbook. I’m happy with the way I’m swinging it. I made a club error on 17, but that’s part of golf. On 18 it was a bad swing off the tee and I didn’t really have much of a second shot.
“That’s golf. Sometimes you get a break and sometimes you don’t, but I’m really happy with the score.
“This golf course is all about being patient and picking and choosing your spots to be conservative, be aggressive. I think my best golf is still ahead of me, which is nice to say at 37.”
Seventy-seven players made the cut at five over par, but that number did not include defending champion Pernilla Lindberg, who had rounds of 73 and 78.