Seeking her fourth LPGA Tour victory of the year, the 23-year-old from Thailand was bogey-free after 36 holes at Hoakalei Country Club on Friday (Saturday AEST).
"It was lucky for us to not have that much gusts," Thitikul said after mostly calm afternoon conditions followed rain and wind early in the opening round.
Germany's Polly Mack also closed with a birdie on 18 for a 65 to match Thitikul at 12-under 132.
Italian golfer Carolina Melgrati (68, 65) and South Korea's Ina Yoon (66, 67) were a stroke back.
First-round leader A Lim Kim (69), who won this event in 2024, was 10 under with Michelle Zhang (67).
Japanese pair Nasa Hataoka (65) and Miyu Yamashita (67) were nine under.
Choi was the leading Australian at seven under, five shots behind the leaders.
Choi followed up her first-round 68 with a 69 on Friday to be sitting in a tie for 14th place.
Grace Kim was one shot behind her compatriot Choi at six under, sharing 22nd place after shooting a 69 in each of the first two rounds.
Cassie Porter (73, 68) and Gabriela Russels (71, 70) were the only other Australians to make it to the weekend, both in a tie for 57th place at three under.
Steph Kyriacou (70, 72), Hanna Green (73, 70) and Momo Sugiyama (74, 70) all missed the cut.
Defending champion Youmin Hwang of South Korea recovered from an opening 72 by shooting 66, leaving her tied for 22nd place.
The tournament leads to a month of events in Asia, starting with the Buick LPGA Shanghai from October 15-18.
- with AAP, Reuters
