The 23-year-old Sydneysider was in for a rough day after making two bogeys in her opening three holes before fighting back with three birdies to join the biggest names in women's golf in the field.
Porter's one-under 69 moved her into a tie for ninth alongside world No.1 Nelly Korda and No.2 Jeeno Thitikul, and they are all now just three behind co-leaders Ina Yoon, Chella Choi and Rio Takeda.
Choi bogeyed her final two holes that blemished an otherwise flawless round.
Korda had 15 pars in her bid to win a third straight tournament. Korda won The Chevron Championship for her third major and the following week in Mexico before taking off last week.
Thitikul, who won last week in the Mizuho Americas Open, also had a 69. It was the same score as Korda but achieved far differently.
Korda had two birdies against one bogey at Maketewah Country Club, in its first year hosting the LPGA Tour event. Thitikul had five pars, seven birdies and six bogeys.
Choi was at six under until her foot slipped on a shot at No.8, leading to her first bogey. She failed to get up-and-down from a bunker on the long par-3 ninth, her final hole.
"Super hard golf course," Choi said. "Fairways very narrow and the green is ... green in not flag, like so many bumps here."
Jin Young Ko and Lilia Vu, both with multiple majors in their careers, were at 67. Another shot behind were Lydia Ko and Charley Hull.
Lydia Ko was in a group with Korda and Thitikul.
"Somebody asked me who I was playing and I was like, 'I'm playing with 1 and 2, and they're almost like 1 and 1,'" Ko said. "I was thinking some part in my back nine how impressive they've played these last few years. I think that's the most impressive thing."
"Jeeno, she's won a couple times, but she also has put herself in contention a lot in the times she didn't win," she added. "Nelly hasn't finished worse than second place this year. So it was cool to be out there with them."
Robyn Choi (71) and Hira Naveed (76) are the only other Australians in the field.
with AAP
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