Defending champion Nelly Korda missed a pair of birdie opportunities on the back nine at Liberty National and settled for a 68, leaving her only two shots behind as the No.1 player in women's golf goes for her first win of the year.
Australia's Steph Kyriacou could not keep pace in her bid for a first LPGA title after starting Saturday one shot from the lead.
She posted a 73 with three bogeys as she dropped to a share off 13th, eight shots off the lead, with countrywomen Minjee Lee (72) and Hira Naveed (73) a shot further back.
Fellow Australians Hannah Green (75) and Grace Kim (75) struggled and were tied 35th at even par, with Gabriela Ruffels (76) another stroke behind, while Karis Davidson (81) was at eight over.
The LPGA Tour moved up several tees to account for wind strong enough to bend flagsticks, particularly on the closing stretch. That led to some big finishes as players positioned themselves for the final round.
Thai star Thitikul was among those who took advantage in a round including nine birdies. She birdied the reachable par-4 16th with water down the right side, picked up another birdie on the 17th and finished at 14-under 202.
"The strategies for today, I just trying to keep it on the fairway and then on the green," Thitikul said. "I know it's going to be a really tough day and then I have to be patient out there. So I don't know how I did that, but like I take it."
Boutier rolled in a 40-foot birdie putt over a ridge on the 15th — that was a bonus — for the start of three straight birdies. She made par on the 18th for a 66.
Korda tried to keep pace with Thitikul and rolled in a 15-foot birdie putt from just off the green at the par-3 14th.
With the wind at her back, she judged her wedge perfectly to 4 feet for birdie at the 17th.
"You just have to dial in to a small target and you have to be focused 100 per cent on each shot," Korda said of the tough conditions, rain Friday and wind on a clear Saturday.
Andrea Lee had her third straight 68 and joined Korda at 12-under 204. Yealimi Noh chipped for eagle on the 16th and shot 67. She was three shots behind.
