Ssumday began his professional career in Korea on KT Rolster as their toplaner, before moving to North America where he spent a year with Team Dignitas, after which he signed with 100 Thieves in 2018.

[3] At Worlds, KT took first place in their group with a 5–1 record and advanced to the knockout stage where they faced a fellow Korean team in Koo Tigers, and were defeated 1–3, exiting in the quarterfinals.

[13] In their first split, the Thieves took first place in the regular season, and made it to the LCS finals, before they fell 0–3 to Team Liquid.

[14] In summer, Ssumday picked up another First Team All–Pro,[15] and the 100 Thieves qualified for the 2018 World Championship,[16] but bowed out in the group stage with a disappointing 2–4 record.

[17] The team struggled in 2019[18] and 2020,[19] staying near the bottom of the standing in the LCS, before making a comeback in summer of 2021, after Ssumday acquired his green card, granting him residency in the United States.