Need help with a thesis.

Hamlet who is young and emotionally unstable should not attempt to avenge his father's death based on what a ghost has to say. Is this good?
- the question is "Something is rotten in the state of Demmark" Develop Thesis based from the quote.

I wonder how much you intend to write. That is one of the issues that Hamlet's friend is worried about, but it seems to me you are avoiding what is rotten.

INCEST
MURDER
Stealing the crown
Mom's lack of grieving for recently departed dad (the ghost).
Hamlet's instability

I am reminded of a similar red flag from Shakespeare...beware the ides of March. In Hamlet Shakespeare is dealing with what is wrong with Mankind, it seems to me. Who knows what evil lurks in the heart of Man? Shakespeare does, and lays it out.

If you have the energy, and time, you might want a thesis that develops this inherent evil in Man's heart, and in that evil, something is wrong.

You might recall the blood that was spilled in McBeth also.

If you don't have the energy for all that, then I recommend you stick to is the ghost evil, or good, for Hamlet. Sometimes the insane (Hamlet) can right injustices.