World number three Stacy Lewis held on to her three-shot overnight lead after round two of the Honda LPGA Thailand on Friday, but was pushed hard by Thai teenager Ariya Jutanugarn who hit a flawless 66.
Teeing off last, American Lewis quickly showed Thursday's stunning 63 was no fluke when she notched a birdie at the par-five first.
She added four more birdies over the day, marred by two dropped shots, which sent her back into the clubhouse with 69 and a healthy 12-under par score overall.
But the day arguably belonged to 17-year-old Ariya, who was six shots behind the leader at the start of play but halved the deficit with a stunning 66 on the back of some hot putting which gave her six birdies.
She will pair up with Lewis on Saturday in front of the home crowd at the Siam Country Club in Pattaya.
"It's always hard to follow up a really good day. I definitely left a few out there," Lewis said.
"I didn't hit it as good today but I made some putts on the back nine and still have a three-shot lead, so I can't complain.
"I think tomorrow is going to be even crazier being in the last group and she's (Ariya) kind of the rising star from here, and I think she's going to be a great player. You have to watch out for her just like anybody else."
Spain's Beatriz Recari was joined by Korean So-Yeon Ryu and Scottish veteran Catriona Matthew poised just four shots off the pace on 136.
Recent graduate So-Yeon Ryu, who has already collected more than $1.2 million career earnings, spared a few words for her university after her flawless 68, revealing she carries its logo on her watch for inspiration.
"So it's all about my university. I think my university give me a lot of energy," she said.
Elsewhere, 15-year-old New Zealand amateur Lydia Ko had a mixed round but ended on an a promising 140.
She was three shots ahead of world number one Tseng Yani, who bounced back after a miserable first day with four birdies to finish on 143, a distance from the leader but a major improvement from a dismal round one.
The day's biggest disappointment was Frenchwoman Karine Icher who stalked Lewis on day one, going home three behind. But Icher posted one of the worst second rounds with a 77, which gave her 143 overall.