At the age of seven, Sung and his family, moved from South of 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 at San Diego to study both computer engineering and economics but dropped out of college in order to become a full-time professional poker player.
Sung has finished in the money ten times at the (WPT), most notably making three of the six player final tables his first two were at the WPT Season VI where at the €7,500 WPT Spanish Championship he finished in 4th earning €117,400 ($164,943) then at the Bay 101 Shooting Star where he was the runner-up to Brandon Cantu, earning $585,000.
In Season VII of the WPT Sung again made a final table at the Doyle Brunson Five Diamond World Poker Classic (the same event he finished 9th in Season V), this time finishing in 4th place earning $396,205. Sung has nine (WSOP) cashes, making five final tables. His first two were at the 2007 WSOP where he finished 3rd in the $1,500 Seven-Card Study event earning $51,222 and placing 9th in the $10,000 World Championship Pot Limit Omaha event, earning $50,177.
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.
Less than two weeks later, Sung took 3rd in the $10,000 2-7 Lowball Championship for $112,041. As of 2013, his total live tournament winnings exceed $4,500,000.
His 9 cashes at the WSOP account for $1,061,518 of those winnings.
The next year at the 2008 WSOP he made the final table in the $5,000 Seven Card Study Hi-Low World Championship where he finished 7th, earning $46,001 in a final table made up of professional such as Annie Duke, Marcel Luske, Chris Ferguson and the winner of the event Sebastian Ruthenberg. Sung also finished in the money at the 2007 WSOP Main Event where he finished in 291st out of 6358 entries which was won that year by Jerry Yang. At the 2009 in the $1,000 Number-Limit Hold"em event Sung won his first bracelet earning $771,106.
