Park, who won both the LPGA money title and Vare Trophy last year, had six birdies in her first 11 holes Sunday and finished the tournament at 12-under 276.
At the time she was two strokes behind third-round leader Ariya Jutanugarn but the Thai teenager suffered a triple-bogey 8 at the final hole. That included missing a 3-foot putt that would have forced a playoff with Park. Jutanugarn ended up second at 11-under.
The win marked the eighth professional title for Park, with four of the victories coming on the LPGA Tour. She has four titles overall in the last year.
Two-time defending Thailand champion and No. 1-ranked Yani Tseng had the tournament's best round Sunday, opening with an eagle en route to a bogey-free 9-under 63. That pulled her into a third-place finish at 10-under, tied with Stacy Lewis and Beatriz Recari, who each shot 70 Sunday.
Park began her final round with a birdie and added others at Nos. 5, 7 and 9 in making the turn at 4-under. She pulled close to Jutanugarn with back-to-back birdies at 10 and 11 before the bogey at the par-4 14th. She was 3-over on that hole for the week.
Jutanugarn shot a very unconventional even-par 72. She had birdies at 1 and 5 before a bogey at the eighth hole. She made a hole-in-one at the par-3 12th and followed that with a birdie at 13. She was still up by two after a bogey at the 14th hole.
Park closed with a series of pars before Jutanugarn came to the 18th. A poor lie after her second shot led to a drop and her fourth shot went over the green. Her seventh shot -- the 3-foot putt -- lipped out, giving Park the title.