Song acted mostly on a freelance basis in Singapore in her early career, and was the female lead in the second season of Heartlanders, as well as the first season of Achar, which won bronze medal at the New York Television Awards and has since been sold to 10 countries. Another show that Steph was in titled ” Singapore Short Story Project” won best Drama Series at the Asian Television Awards in 2004.

In 2004, Song joined SPH MediaWorks, and was supporting lead in “Perceptions” and female lead in the very last Channel i-produced drama Six Weeks which won Best Drama Series at the Asian Television Awards 2005. When MediaWorks merged with MediaCorp later that year, Song did not move over to MediaCorp choosing instead to move to North America, where she found success, nominated 6 times in the last five years for her work as female lead actress on features Dim Sum Funeral, The Thaw, Paradox, the CBC's miniseries Dragon Boys, War, and two Douglas Coupland written projects: Everything's Gone Green and, more recently, the 2008 TV series jPod.

Song is currently represented by Echelon Talent Management Inc.

She portrayed the character of Roulette on The CW's Smallville.