Chanettee Wannasaen, chasing her second LPGA title, closed with a birdie to seize a three-stroke lead after Saturday's third round of the Dana Open.
The 20-year-old Thai fired a five-under par 66 to stand on 16-under 197 after 54 holes at Highland Meadows in Sylvania, Ohio.
"Today was a really good day," said Chanettee. "I'm not going to think about the result because I don't want to get stress for tomorrow. Just stay in the present, don't think about the future."
South Korean Ryu Hae-ran was second on 200 after closing with back-to-back birdies at the par-5 17th and 18th holes to shoot 65.
"I made some lot of long putts and made a lot of birdies on the tricky holes, Ryu said. "That was good today too."
Sharing third, five strokes adrift, were Taiwan's Cheng Ssu-Chia, who birdied four of the last six holes to shoot 66, China's Lin Xiyu, who birdied four of the final five to fire a 70, and defending champion Linn Grant of Sweden.
Chanettee, ranked 43rd, won her only LPGA title at last September's Portland Classic as a Monday qualifier.
This year, she was third at the Americas Open in May and shared eighth at last month's Dow Championship.
Chanettee birdied the par-3 second and par-4 ninth holes then reeled off three birdies in a row before making her lone bogey at 16 and answering with a birdie at 18.
Ryu, last year's LPGA Rookie of the Year, won her only LPGA title at last October's Northwest Arkansas Championship. She has six top-10 showings this season, including fifth at last week's Evian Championship.
Lin, the highest-ranked player in the field at 15 in the world, seeks her first LPGA crown in her last Olympic tuneup while Grant is also in her final event before playing for gold in France.