2013 he has been nominated for the World Championships in adult area for the first time. In the singles he doesn't won a medal, but became vice-champion with Park Young-sook in the mixed doubles. 2015 where he played a WTTC again, he reached the third place in the doubles. Since August 2015 Lee is under the top 20 players in the world. At his first team WTTTC he reached together with the team place 3 (Bronze).