Ha was born in Seoul. His father was a member of the national basketball team and his older sister is a member of the national basketball team. His height was 2.18 m in middle school when he won the championship. Lots of universities wanted Seung-Jin to sign with their school. He decided to play for Yonsei University and won the university championship with them. He decided to go pro and signed with the Portland Trail Blazers in 2004.