He is best known for being the founder, chairman, and chief executive officer of Singapore-based combat sports promotion ONE Championship.

To put himself through Harvard Business School, Sityodtong delivered Chinese food and taught Muay Thai to make ends meet before graduating with his MBA in 1999.

[5] Chatri started Muay Thai as a child under Kru Yodtong Senanan of Sityodtong Camp in Pattaya, Thailand.

He earned his blue and purple belts under the Renzo Gracie banner from BJJ World Champions Rafael Gordinho Lima and Leandro Brodinho Issa respectively.

With Renzo Gracie's blessing, BJJ World Champion Alex Silva awarded Sityodtong his brown belt in 2021.

[10] In 2024 Renzo Gracie awarded Sityodtong his BJJ black belt live on air at ONE 168 in Denver, Colorado.

[21] In August 2022, Sityodtong accepted an invitation by the Royal Thai Army to become a promoter at the prestigious Lumpinee Boxing Stadium in Bangkok, Thailand.