He started boxing in 2020 under Surachart Pisitwuttinan's Nakornloung Promotion, which has already featured world champion boxers including Veeraphol Sahaprom, Srisaket Sor Rungvisai.
Thananchai was able to defeat many skilled Thai boxers were Kompayak Porpramook, Eaktwan BTU Ruaviking, Samartlek Kokietgym.
He was able to defeat Kento Hatanaka, WBO Asia Pacific flyweight champion by unanimous decision via 12 rounds.
The event was held on October 13, 2024, at Tokyo's Ariake Coliseum as part of a world championship quadruple-header that saw the main event Seiya Tsutsumi defeated fellow-countryman Takuma Inoue to win the WBA bantamweight title after the pair traded blows for 12 action-packed rounds, and Kenshiro Teraji TKO Nicaragua's Cristofer Rosales in the 11th round for vacant WBC flyweight champion, with Shokichi Iwata TKO Spain's Jairo Noriega in the third round for vacant WBO light flyweight crown.
[3] After the match, Akui gave an interview saying that even though he won, it was not a perfect victory because Thanachai was able to fight and counter him well throughout the 12 rounds.