Porter, 20, and Yoktuan signed for six-under rounds of 66, with Queenslander having shrugged off the nervous prospect of playing in the same group as two legends and former World No.1s – Karrie Webb and Jiyai Shin.
She made four birdies and holed a long bomb for eagle on the par-5 5th hole, Porter then calmly rolling in a two-metre par putt at the 18th hole to maintain her share of the lead.
Shin, the winner of two AIG Women’s Opens, shot five-under 67 while Webb carded an opening 72, even-par, with two late birdies.
American Emma Talley, New Zealand amateur Fiona Xu, Japan’s Shina Kanazawa, Shin and another South Korean, Min A Yoon, are all at five-under tied for third with Shin.
Poter, Shin and Talley the only members at the group at five-under and better to play the more difficult Beach Course on Thursday.
“I had so much fun out there,” Porter said afterward. “With two former World No.1s and major champions, what a group. I was so pumped last night. So it’s really nice to come and put a score on the board.
“I had nerves all day if I’m being honest, but it kind of worked for me. I used it to my advantage, I guess, and kept on top of everything which is nice.”
Seven players share eighth at four-under, including LPGA bound Aussie Grace Kim, last week’s TPS Murray River winner Sarah Jane Smith and teenage amateur Sarah Hammett.
Kim’s fellow LPGA players Su Oh and Karis Davidson part of the group at three-under sharing 15th.
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