Park took advantage of a missed putt of 3½ feet by American Lizette Salas at the 72nd hole, holing from eight feet herself at the first extra hole after Salas had missed from slightly longer range to secure the title.
It's Park's 5th win on the LPGA Tour and comes after victories earlier this year at the Volunteers of America LPGA Texas Classic and the KPMG Women's PGA Championship.
The 24-year-old previously held the women's number one ranking in November last year for just one week before Shanshan Feng claimed the mantle.
Park also won two titles in 2017 including a maiden major win at the US Women’s Open and the CP Women's Open en route to her Rookie of the Year title.
Salas was chasing her second LPGA Tour title and appeared to have the title in her grasp leading by one with two holes to play but she followed a bogey at the 71st hole with her missed birdie opportunity at the last.
Amy Yang finished 3rd and only one shot from the playoff but she gained even more admirers with a decision to ignore a ruling from a tournament marshal as to where her ball crossed a hazard at the par-three 7th and drop considerably further back.
The resultant double bogey would eventually cost her a chance at the playoff but her gesture to follow her gut and integrity is a further example of the standing she has as a player and individual on the LPGA Tour.
Rookie of the Year and Women’s Australian Open champion Jin Young Ko finished alone in 4th position and further cemented her claims to the Louise Suggs Rookie of the Year title.
LPGA Tour rookie, Hannah Green, finished as the leading Australian in a share of 28th but a disappointing weekend on the low scoring layout proved costly.
Katherine Kirk was 39th, while Sarah Jane Smith, Minjee Lee and Rebecca Artis missed the cut.
GEORGIA HALL: 'NO-TAKEAWAY' PUTTING WARM-UP
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.