Koh joined
FC Seoul, then known as the Anyang LG Cheetahs, in 2003. In 2015 he moved to
Al-Rayyan. In September 2019, he moved to
Slaven Belupo in Croatia, but left the club two months later. He moved back to South Korea to join
Ulsan Hyundai FC ahead of the
2020 K League 1 season. In his first season with Ulsan, he helped them win the
2020 AFC Champions League for the second time in the club's history. == International career ==