Jee Young Lee, Jiyai Shin and Candie Kung finished in a share of third one shot behind Park.
"This La Costa is a great course and I must thank Kia and Jo Golf for the invite to play here," said a delighted Seo after her emphatic victory.
The leader of the 2009 Korean LPGA Tour money list and a winner of five events there last season, Seo recently played at the ANZ Ladies Masters in Australia where she finished 4th behind Karrie Webb.
The victory will earn Seo the right to play on the LPGA Tour and given her success in what is the breeding ground of Korean ladies golf, the KLPG Tour, she seems destined to quickly add to this first victory.
Seo started the final round with a five shot advantage and even an opening bogey could not shake her from the job at hand. She added three birdies before the turn and with her nearest rivals heading into day four not able to add any real pressure it was left to Park to win the fight for second position.
Park was the 2008 US Women's Open Champion but there has not been much to get excited about since. She did however finish runner up in Japan on two occasions earlier this year, one of those in rather controversial circumstances having been penalised when her ball moved while over her putt at the final hole.
The leading Australians were Tamie Durdin and Katherine Hull in 31st position although that will be of little consolation to Durdin who let a great chance of a good finish slip with a final round of 79. It was Durdin's first start on the LPGA Tour since 2003 having regained her playing privileges for the LPGA Tour via LPGA Tour School late last year.
Karrie Webb was 39th and Lindsey Wright 57th.
The LPGA Tour now moves to their first major championship of the year, the Kraft Nabisco in Rancho Mirage in California.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.