Concerning authorial voice or intrusion into the text of Shakespeare's Hamlet, I'm afraid you're pretty much out of luck. Hamlet is a play, not a work of fiction or narrative poetry. Every word spoken is spoken by a character, not by the author. Therefore, no authorial voice exists in the play.
There's not even a chorus that one might suggest provides authorial intrusion.
I'm afraid the best you may be able to do is to point to the advice the character Hamlet gives to the Players about acting, after they arrive in Elsinore. Some commentators have seen Shakespeare's advice in Hamlet's advice. Even this, though, is speculation, and the text is still technically dialogue spoken by a character, not authorial intrusion.