The Thai world No.2 pulled away with a pair of late birdies in a final-round three-under-par 69 in New Jersey to win by four shots at 13 under over China's Ruoning Yin as Australian Hannah Green was unable to mount a Sunday charge.
Thitikul had her third-round two-stroke lead cut to one before the turning point came with a two-shot swing on the par-3 16th hole as Yin made a rueful bogey.
Thitikul also won the Honda LPGA Thailand earlier this year and now has nine career LPGA titles. This is her fourth season with multiple wins since joining the LPGA in 2022.
The victory also draws the 23-year-old closer to American Nelly Korda, who regained the world No.1 ranking from Thitikul last month and took this week off following consecutive wins.
"For me, world ranking or top players doesn't really define what I'm doing," Thitikul said after earning the $US487,500 ($A674,000) winner's checque.
"I'm just trying to just do my best out there, trying to be as consistent as I can, because I know it's going to be a really tough competition in and out every week, on and off every week, and different courses."
Yin shot a 69 to finish alone in second.
Frenchwoman Celine Boutier, who played in the final group with Thitikul, had three bogeys and no birdies on the front nine to fall out of the chase. She shot 75 and tied for ninth.
Chasing a fifth win of 2025 after starting Sunday four shots back in a tie for fourth, Green carded a disappointing final-round 75 to share 14th spot at three under.
Fellow Australian Grace Kim (71) tied for 20th, a further two strokes back.
Karis Davidson and Robyn Choi both posted Sunday 73s to finish joint 39th at two over, one shot ahead of Cassie Porter (71).
With AAP
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