1. Professional career
Hong Seong-yo's professional football career spanned several clubs within South Korea, where he was consistently deployed in a defensive role.
1.1. Club career
As a professional footballer, Hong Seong-yo played for three notable South Korean clubs. He was formerly part of the Chunnam Dragons roster. Following his tenure there, he joined Gwangju Sangmu, a club known for its association with military service. Later in his career, Hong Seong-yo also played for Busan I'Park. Across these clubs, his primary position remained that of a defender, contributing to their respective defensive lines.