In 2008, the Korean was runner-up to Yani Tseng by 267 points in the race for Louise Suggs Rolex Rookie of the Year honors on the strength of nine top-10 finishes; recorded season-best runner-up finishes at the Sybase Classic Presented by ShopRite and the Evian Masters, where she lost to Helen Alfredsson in a three-hole, sudden-death playoff; carded a season-low 65 in the second round of the P&G Beauty NW Arkansas Championship, where she tied for eighth; crossed the $1 million mark in season and career earnings at the Samsung World Championship.
In 2009, Choi became a Rolex First-Time Winner at the Samsung World Championship, where she recorded a career-low 63 in the third round and crossed the $2 million mark in career earnings. She also won the Hana Bank - KOLON Championship 2009 for her second career victory and finished in the top-10 nine other times.
In 2010, she won the LPGA Hana Bank Championship Presented by SK telecom by 2 strokes with a final score of 10 under par. She also finished tied for second at the LPGA State Farm Classic, U.S. Women's Open, Evian Masters Presented by Societe Generale and Safeway Classic presented by Coca-Cola. Throughout the 2010 season she managed to achieve an impressive 15 top 10 finishes.
Earned her fifth-career LPGA victory at the 2011 Sime Darby LPGA in Malaysia. Finished second in the race for the Vare Trophy with a scoring average of 70.53. Other top-10 finishes included: second at the Safeway Classic Presented by Coca-Cola where she lost in a playoff to Suzann Pettersen, second at the LPGA HanaBank Championship, third at the Sybase Match Play Championship and the Mizuno Classic; tied for third at the Avnet LPGA Classic; tied for fourth at the CME Group Titleholders; tied for fifth at the Kia Classic; finished sixth at the HSBC Women's Champions and the CN Canadian Women's Open; tied for seventh at the Ricoh Women's British Open; tied for 10th at the Walmart NW Arkansas Championship. Also won the Hanwha Finance Classic on the KLPGA.
No 2 in the world Choi won her first LPGA major in 2012, The US Women’s Open. She also earned her seventh career win at the season-ending CME Group Titleholders and made 21 cuts.