Smith moves closer to becoming a two weight world champion
The fight was on the undercard for the heavyweight clash in the Saudi Arabian city between Ukraine's WBA, WBO, IBF and IBO champion Oleksandr Usyk and Britain's Anthony Joshua.
Smith, who moved up a weight after losing his WBA super-middlewight title to Mexican Canelo Alvarez in December 2020, floored the Frenchman with a punishing left hook to the head in the fourth round.
Smith now becomes mandatory challenger for the WBC title held by Montreal-based Russian Artur Beterbiev, who also holds the IBF and WBO belts.
Beterbiev was due to defend his titles against Britain's Anthony Yarde in late October but Boxing Scene reported this week that the Russian was injured and would not fight again until 2023.
"Tonight I'm probably one step closer," said Smith after his win in Jeddah's King Abdullah Sports City Arena.
Promoter Eddie Hearn said Smith needed to stay active before any title fight.
"The only thing he's in the game for is to be a two division world champion," he said. "We want him to box again if he's ready and willing in probably November and December because Beterbiev is probably going to come in the spring."
Hearn said he would like Smith to fight Beterbiev at Liverpool's Anfield stadium.