How do I maintain MD state residency after selling house and have gone on a long extended stay overseas?

If you are not in the state for 1 or 2 years and have no home that you maintain that you would be going back to, you would not be able to maintain residency for tax purposes in that state.  

This simply means, you would not need to file an MD return for the years you are gone.

Is there a reason you want to maintain residency?