The 20-year-old, who turned pro in 2020 and won her first three China LPGA starts, had a 12-under par total of 199 at Palos Verdes Golf Club while South Korea’s Kim — who started the day tied for the lead with Yin — posted a 69 for 201.
Kim, whose five LPGA victories include a major title at the 2014 Evian Championship, pulled away early with three birdies in the first seven holes.
Yin was three down after a bogey at the eighth that put her at even par for the day and from there, she said, “I just told my caddie, man we’ve got to trust the line and just putt it.”
After she followed a birdie at the ninth with a bogey at the 10th, Yin hit her stride with three straight birdies at 12, 13 and 14 to seize a one-shot lead.
She added one more birdie at the 16th, where her shot into the green left her less than two feet.
Yin said her plan for Sunday was to “just play my game. I know I can make birdie, just be patient, that’s my thoughts.”
While a first LPGA title would mean a lot “not just for me but also China golf,” Yin said she didn’t expect to be nervous once she’d teed off on Sunday.
“After that, just pretty normal,” she said.
Kim couldn’t maintain her early pace, posting a birdie and two bogeys coming in.
“On the front nine, the putter was working really well, but my shots weren’t really on par with my putter, so I was kind of busy with my recovery shots,” she said. “Hopefully the shots tomorrow will be better than today’s.”
Georgia Hall, coming off a runner-up finish to Celine Boutier in a playoff in Arizona last Sunday, had two eagles in a stunning nine-under par 62 that left her alone in third on 203.
Hall’s seven-under front nine included eagles at the fifth and seventh sandwiched around a birdie at the sixth — with birdies at the first and ninth for bookends.
“I think I was even six-under after seven, which was crazy,” Hall said. “Just had to kind of forget about the previous holes and really stay focused otherwise I could have just like parred in.”
She picked up two more birdies on the back nine to match her personal best score of nine-under.
“Very happy with today,” Hall said. “I don’t normally write down ‘two, two, three’ on the scorecard.”
Her first eagle came at the fifth, a driveable par-four where she chipped in.
After a birdie at the sixth she reached the green at the par-five seventh in two using a driver for the second shot and giving herself a five-foot eagle putt.