Yes you can but its probably going to be in a different area. After he faints, he will not appear for a while. He will then suddenly start to show up in random different areas, not in the places he appeared in before he fainted. You will just have to be on the lookout for thunderstorms and keep an eye on the boards. My suggestion to catch Thundurus ould be using a Quick Ball on the first go, that's how I got mine.
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yes
No. Once a Pokemon faints you can't catch him. Sorry. No. Once a Pokemon faints you can't catch him. Sorry.
No just save it before you attack and turn it off if it faints
He is gone Dont try to catch him again
Yes you can! After he faints go back and he'll be there.