After winning three LPGA of Korea Tour major championships in 2009, Seo notched her first LPGA Tour triumph at the 2010 Kia Classic where she finished six shots ahead of Inbee Park.[1]
Seo had a close call in the 2011 U.S. Women's Open when she led by two shots with two holes to play, but she missed a 4 footer for par on the 71st hole, while So Yeon Ryu birdied the 72nd hole, resulting in a playoff, which Ryu went on to win.
Seo also came close at the 2012 Kraft Nabisco Championship, where she led by three strokes at one point, but bogeys on the last four holes would result in her finishing two strokes back of winner Sun Young Yoo.
On 30 November 2013, she married Junghoon Philip Kook (born 1979), an executive officer at DWS Asset Management based in Seoul, and gave a birth to their first son, Dohyun Philip Kook on 15 August 2014, on the Independence Day of Korea. Since then, they had two more sons, Dohoon Francis (born 2016) and Doheon Michael (born 2018). Seo officially retired from professional golf in November 2015 to spend more time with her family.[2]