In 2007, Ko batted .268, compiling a career-high 12 home runs, 119 hits and 66 RBIs while appearing all 126 regular-season games.

Ko's big hit in the Olympics was a three-run homer off of Yang Chien-fu in the 8–7 Korean win over Chinese Taipei.

Prior to the 2009 KBO season, Ko participated in the 2009 World Baseball Classic in March 2009.

In the WBC, he batted .308 with 4 hit in 13 at-bats, sharing the starting second base position with Jeong Keun-woo.

In Round 2, Ko smacked a solo home run off New York Mets starter Óliver Pérez in the bottom of the 5th inning to lead his team to an 8–2 victory over Mexico.