 Seo played for South Korea under-23 at the 1992 Summer Olympics in Barcelona, and went into the opponents' goalpost with a goal during the match against Sweden.He was reportedly offered a contract from FC Barcelona and other European club giants after his performances at the Olympics, but he stayed South Korea to serve a two-year mandatory military service.He also played for South Korea at the 1994 FIFA World Cup, and scored the equalizer against Spain.