Born in Bimbo, Kassaï has played in France for Le Mans B, Rouen, Romorantin and Le Mans. In June 2015, Kassaï moved to Irtysh Pavlodar on loan until the end of the 2015 season. In December 2015, following a successful loan period at Kazakhstan, Slavia Sofia sold Kassaï to Tobol.
Kassaï made his international debut for Central African Republic in 2010, and has appeared in FIFA World Cup qualifying matches.
Bronze medalist in 2018