Which one of the following is correct?

Here are the two sentences

*I've absolutely no frigging idea who is he".

or

“I’ve absolutely no frigging idea who he is.”

Thanks in advance.

‘… who he is.’ is the correct version.

Just in case you don’t already realise it, this is not a polite phrase. Some people could be offended by use of the word ‘frigging’ as it is based originally on a profanity.

Thanks. I saw that sentence in a book.