What is the religious ruling on someone who frequently uses foul language for the purpose of jesting?

The Shari'ah permits jesting with two conditions: truthfulness and moderation. The Prophet himself used to jest but never spoke anything but the truth.

Among the proofs for the prohibition of lying in jesting is his (peace be upon him) saying: "Woe to him who speaks and lies to make people laugh, woe to him, then woe to him."

And if foul language is added to lying, the matter becomes even more serious, for his (peace be upon him) saying: "The believer is not one who slanders, curses, speaks obscenities, or is foul-mouthed."