Lydia Ko shot an 8-under-par 64 in the second round of the Indy Women in Tech Championship on Friday to move into a first-place tie with Lexi Thompson with one round left at Brickyard Crossing in Indianapolis.
Ko and Thompson are at 15-under for the tournament, one stroke ahead of Candie Kung, who also shot a 64 on Friday.
The 20-year-old Ko, a New Zealand resident and former No. 1 player who has not won an LPGA event in 14 months, had nine birdies and one bogey in her round, and she birdied five straight holes in one stretch.
Ko started her round on the back nine, then had consecutive birdies on holes No. 2 through No. 6 on her back nine.
Ko began 2017 with four top-10 finishes in seven events. However, she has not finished higher than 10th in an event since then, and she missed the cut in two of her last three tournaments.
"I've just enjoyed kind of being in this position and being able to hit some good shots and give myself good looks at birdie," said Ko. "When you start doing that, it just builds your confidence."
Thompson, the first-round leader, shot a 6-under 66 in the second round and had to scramble to save par on her final two holes to grab a share of the lead in this three-round event.
"I'm never going to complain with a 6-under-par round, but I didn't really focus on anybody else like Lydia," said Thompson. "I know (Ko) played great today, but I was just trying to go out with the same mindset I did yesterday and make sure I did my routine and commit to my golf shots."
Thompson, who is looking for her second victory this season, had no bogeys and six birdies in her round.
"I always have the same mindset going in to every round, just going out there, just trying to do my best and just focus on my game," said Thompson. "That's all I can control, and my attitude."
Kung is well within striking distance, just a stroke behind the leaders after a round that featured nine birdies and one bogey.
"I've been playing pretty good golf this year but I just haven't been able to put them all together," said Kung, who has not won an LPGA event since 2008. "Being able to put them together last week, four rounds, and then the last two rounds, it feels pretty good."
Three strokes behind Kung is Ashleigh Buhai of South Africa, who stands at 11-under after shooting a 66 in the second round.
Cristie Kerr and Amy Olson are another stroke back at 10-under.
Anna Nordqvist of Norway was among those who failed to make the cut.