"I gave myself a lot of looks for birdies, especially on my back nine, but I just wasn't making many putts," she said. "But hey, I'll take three-under for the first round. It was really solid, and hopefully it's good momentum going into tomorrow."
Ko, who teed off late overnight in her second round, is chasing her first tournament win in 14 months and is coming off a second placing at last week's LPGA event in Indianapolis.
After finishing third or better in five consecutive majors, Ko hasn't claimed a top 10 finish in her last six major tournaments. While in good position, she has ground to make up on Park, one of the form players of 2017, who also took advantage of a remarkable stroke of luck.
Park had been six over through just five holes in the rain and wind before play was abandoned and all scores wiped. The US Women's Open champion regrouped and had seven birdies and an eagle to lead the tournament by two shots.
"I forgot about yesterday and just focused on my play today," Park said, acknowledging she was "surprised" the LPGA scrapped Thursday's play.
Moriya Jutanugarn, of Thailand, is second, while tied for third, three shots back are Australia's Katherine Kirk and Anna Nordqvist, of Sweden, who both carded a 66. Jessica Korda, of the United States, and Women's British Open winner In-Kyung Kim were a further shot back on four-under. Park played in a stellar group with top-ranked So Yeon Ryu (75), her fellow South Korean, and No2 Lexi Thompson (70), of the US. Ryu suffered a six-shot swing having been two-under and sharing the lead with Korda when play stopped.
Jutanugarn and Nordqvist were in the late-starting groups and never had to endure the 70 km/h gusts and driving rain one day earlier.
