American Brittany Lang, who landed her first major title in a playoff for the U.S. Women's Open at CordeValle in July, carded a 67 to end the day level with South Korea's Chun In-gee, Spaniard Azahara Munoz and Swede Dani Holmqvist.
The leading three players in the women's game - top-ranked New Zealander Lydia Ko, second-ranked Thai Ariya Jutanugarn and the local favourite, Canada's world number three Brooke Henderson - all opened with 70s in blustery conditions.
"Pretty good, pretty good," Choi, who won her only LPGA title in a playoff for last year's Marathon Classic, told reporters after mixing seven birdies with a lone bogey in her opening 66.
"A lot of wind today, but my game is good and driving is good, shots were good, so I made a lot of birdies. I worked really hard the last three weeks. I want to hit straight and strong my drive all four days."
Henderson, already a three-times LPGA winner at the age of 18, said the gusty conditions had presented a stiff challenge.
"The wind really picked up on the back nine, it was kind of difficult," the Canadian teen told reporters.
"And you could see all three of us not really playing exactly the way we wanted just because of the wind and the conditions.
"But I finished at two-under ... I'm happy. I'm just excited to tee it up tomorrow when conditions will be a little bit softer and not as much wind."
The highlight of Lang's round came at the par-five third, her 12th, where she holed out with a lob wedge from 70 yards for eagle.
"I actually laid it up a little bit too far left and through; and I was like, 'Awe, should still be okay.' And then when I hit it, it was nice and high and on the right line," Lang said.
"We couldn't see it, and then my husband and all our friends were up there, and they were screaming, so it was a pretty cool reaction."
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)
