At the age of seven, Sung and his family, moved from South Korea to the United States, His interest in poker began when he notice his father playing the game then later Steve would play friends of his while still attending high school, after he graduated, Sung attended the University of California, San Diego to study both computer engineering and economics but dropped out of college in order to become a full-time professional poker player.

[5][6] The next year at the 2008 World Series of Poker he made the final table in the $5,000 Seven Card Stud Hi-Low World Championship where he finished 7th, earning $46,001 in a final table made up of professional such as Annie Duke, Marcel Lüske, Chris Ferguson and the winner of the event Sebastian Ruthenberg.

[7] He also came close to making a six player final table in the $2,500 2-7 Triple Draw event where he finished in 8th place.

[9] At the 2009 World Series of Poker in the $1,000 No-Limit Hold'em event Sung won his first bracelet earning $771,338.

[11] At the 2013 World Series of Poker Sung won the $25,000 No Limit Hold'em Six Handed in field of 175 entries earning $1,205,324, with a final table of notable poker professional that includes, online cash specialist Richard "nutsinho" Lyndaker (6th), Maxi Lehmanski (5th), Stephen "stevie444" Chidwick (4th), Dani Stern (3rd) and the runner-up Phil Galfond.