The 18-year-old Park, making just her fourth LPGA Tour start, showed maturity and composure in difficult conditions at the wide-open Ko Olina Golf Course.
'Everything I looked at went in,' Park said. 'I was so confident (and) very comfortable on the greens.'
Se Ri Pak, who needs to play just eight more events to qualify for the World Golf Hall of Fame this year, made a late move to open with a 67. Meaghan Francella survived a triple bogey and was at 68, along with Kyeong Bae.
Park started strong, birdieing five of the first seven holes and making the turn at 31. She drove into the rough for a bogey on No. 10, but hit a wedge to set up her 7-foot birdie putt on 14 and sank a 25-footer for birdie on the 16th to reach 6 under.
'I felt really comfortable coming out here even though I didn't know half the field,' she said. 'It was nice to see people I've seen on TV and be able to play against them.'
Park earned her first LPGA paycheck last week -- worth $6,625 -- for her 33rd-place tie at the season-opening SBS Open. As an amateur, she tied for 15th at the 2006 Kraft Nabisco Championship, her only LPGA start last year.
After a successful amateur career that included five AJGA wins, Park played on the Futures Tour last year and earned her LPGA Tour card by tying for fifth at Q-school.
'This is what I've always wanted to do. This is my dream,' said Park, a Brazilian-born Korean who grew up in Torrance, Calif., and recently moved to Orlando, Fla.
Prammanasudh started on the back nine had four straight birdies, starting with a 25-foot putt on No. 4, to shoot up the leaderboard and tie Park at 6 under.
'I got some great birdie chances out there and was lucky enough to make a few, so I'm very pleased especially with the wind,' she said.
The former University of Tulsa standout won the 2005 Franklin American Mortgage Championship for her lone LPGA Tour title.
Prammanasudh said took formal golf lessons for the first time in her life during the offseason. She learned the game from her father, who taught himself how to play.
'I just need something that's going to make me really consistent throughout the whole entire year instead of having ups and downs,' she said.
Pak, who won her fifth career major last year in the LPGA Championship, made her move by holing a 30-foot downhill birdie putt on No. 10.
She then hit a knockdown 4-iron tee shot to set up a birdie on the par-3 12th, and followed with short birdie putts on Nos. 15 and 16.
'I feel that I'm ready but I don't feel like I'm mentally ready and really strong,' she said. 'But the wind actually woke me up right away.'
Francella, who spent most of 2006 on the Futures Tour, started on No. 10 and made the turn at 32. After parring No. 1, she went triple bogey-bogey-par-eagle-birdie. She birdied No. 8 to close out her wild back nine.
The scoreboard incorrectly listed Francella at 69 and was corrected more than an hour after her round after she spotted the error on TV.
Jeong Jang, Jee Young Lee, Nicole Perrot and Pat Hurst shot 69s.
Karrie Webb, who moved up a spot to No. 2 in the latest world rankings, opened with a 70. Webb finished third at Turtle Bay last week after starting the year with a two-week Australian sweep. She won her third Women's Australian Open title three weeks ago and added her sixth Australian Ladies Masters victory the following week.
Defending champion Meena Lee shot a 71, leaving her tied with LPGA player of the year Lorena Ochoa and Ai Miyazato, who had a team of photographers from her native Japan following her every move.
Last year, Lee won the inaugural Fields Open for her second tour title, holding off Michelle Wie in regulation and beating Seon Hwa Lee on the third hole of a playoff.
Paula Creamer, who won the SBS for her first LPGA title in 19 months, opened with a 72.
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