Nicknamed The Korean Hawk, he defended his WBC Light Flyweight Championship a record 16 times. He compiled a career record of 38-4.
One of his first professional fights was against WBA flyweight champion Alfonso Lopez.
He became the first Korean boxer to be inducted into the International Boxing Hall of Fame.
His wife left for America with all his money in 1988.
He and Japanese fighter Koki Kameda have both won the WBC Light Flyweight title.