Oh competed at the 1988 Summer Olympics where he was a favorite to medal, however, he was eliminated in his first bout by a narrow 3–2 decision against eventual silver medalist and future hall of fame champion Michael Carbajal. Oh had defeated Carbajal by a 3–0 margin in a previous meeting.[3]
In February 1990, Oh made his pro debut in minimumweight, and after only six fights challenged Ricardo Lopez for the WBCminimumweight title on January 31, 1993. However, he was TKO'd in the 9th round. Oh had struggled to make weight to minimumweight, and eventually retired after the bout with a record of 6-1-0 without moving up a weight class.