[4] In his second season, Choi couldn't concentrate on his club by playing for Olympic team, and scored only one goal during 19 league appearances.

He was loaned out to J1 League club Kashiwa Reysol ahead of the 2005 season, but didn't make the reversal of his flow for five months.

He also left a memorable game against Al-Shabab in the 2006 AFC Champions League, where he led Ulsan to a 6–0 victory by destroying opponents' defense as well as scoring two goals.

[7] Choi went on a trial at Championship side Sheffield United after the end of the 2007 season,[8] but the club decided against signing him.

[14] He denied his involvement when media reports raised the allegations about throwing matches,[15] but soon admitted it as the scandal deepened.

[19] It was announced that Choi would join Macedonian club Rabotnički on 16 January 2012,[20] but following investigation, FIFA imposed on him a lifelong ban from all sports.

[22] While at Jeongmyeong High School, Choi was called up to South Korean under-17 team for the 1998 AFC U-16 Championship, and scored two goals in six appearances.

[25][26] In March 2003, Choi was called up to the senior national team for the first time, and made his debut in a 0–0 draw against Colombia.

[37] It was reported on 9 February 2012 that Choi was sentenced on probation for two years and 200 hours of social services for ten months as a result of his actions, relating to match fixing.