South Korea's Kim Hyo-Joo fired seven birdies without a bogey Saturday, her third-round 64 giving her a three-shot lead over Lydia Ko and Alison Lee in the LPGA Marathon Classic in Ohio. Kim, who held a share of the lead after each of the first two rounds, was on fire on the Highlands Meadows course in Sylvania. Her first birdie of the day, at the par-four fifth, sparked a run of five birdies in seven holes that featured three straight at the seventh, eighth and ninth. "I hit good drives, good tee shots and iron shots, and I managed to get up-and-down, and I made good putts," said Kim, who celebrated her 21st birthday Thursday. "It was good." Birdies at 14 and 17 saw her build a comfortable cushion heading into Sunday's final round on 15-under par 198. New Zealand's world No. 1 Ko, who started the day with a share of the lead, also played without a bogey but could come up with only four birdies in a 67 for 201. That left her tied for second with American Alison Lee, who notched her second straight 66. They were one stroke in front of Thailand's Ariya Jutanugarn, who carded a 66 and American Stacy Lewis — who had six birdies without a bogey in her six-under 65. Ko was left regretting a short miss at the par-five 18th that would have moved her closer to playing partner Kim. "I let one — it was a very dumb one — slip on the last hole," she said. "But it was a pretty consistent day. There were so many putts that were so close but didn't end up falling, so hopefully a few more fall (Sunday). "Hyo-joo played great today, holed a lot of putts, put herself in really good positions, so yeah, obviously I'll be trying to track her down tomorrow, but there's still a lot of golf to be played." After tricky winds made for tough scoring Friday, Ko said conditions couldn't have been better for the third round. "If it stays like this to tomorrow, I'm pretty sure there could be some low (scores) out there," said the 19-year-old star, who won her second major title at the ANA Inspiration this year. Lee notched three of her six birdies in her last four holes. "I just felt really in tune with my swing," Lee said. "All my approach shots, I was hitting it well. Putting felt really good today. I did miss a couple putts, but other than that, I felt like just overall I was hitting it really solid."