I'm not a teacher, so this could be way off mark, but - I think that other students will have noticed this guy too and be moderately annoyed at him. I think it's safe for you to single him out and give him special rules, without having the rest of the class worry if they're next. Just make it clear that you've been patient with him for a long while now, but even you have some limits.

As for the special rule, I think a "cooldown" would be effective and not very harsh. Basically, after he asks a question, he needs to wait for at least 5 minutes before asking another. Or maybe you give him 2 or 3 questions, and after he's out, then he needs to wait.

In addition you could make it clear that he can write them all down and you'll answer them after the lesson in private.

Having the questions rationed like that will make him think twice about what is really important to ask. Making him write them down will help notice the repetitive ones.

Or maybe he's just too lazy to bother, in which case nothing will help him anyway and the cooldown will just keep the rest of the group running smoothly.

Or, as suggested in another question, he might have some sort of mental disability - it's probably worth checking that out too, before taking any other action.

I'm not a teacher, so this could be way off mark, but - I think that other students will have noticed this guy too and be moderately annoyed at him. I think it's safe for you to single him out and give him special rules, without having the rest of the class worry if they're next. Just make it clear that you've been patient with him for a long while now, but even you have some limits.

As for the special rule, I think a "cooldown" would be effective and not very harsh. Basically, after he asks a question, he needs to wait for at least 5 minutes before asking another. Or maybe you give him 2 or 3 questions, and after he's out, then he needs to wait.

In addition you could make it clear that he can write them all down and you'll answer them after the lesson in private.

Having the questions rationed like that will make him think twice about what is really important to ask. Making him write them down will help notice the repetitive ones.

Or maybe he's just too lazy to bother, in which case nothing will help him anyway and the cooldown will just keep the rest of the group running smoothly.

Or, as suggested in another answer, he might have some sort of mental disability - it's probably worth checking that out too, before taking any other action.