What are the rights for tenant and landlord if there is no rental (=expired) agreement, e.g. regarding rent and return of safety deposit (from already expired rental agreement)?

You need to talk to an attorney but I would thank that both renter and landlord wold be covered under the expired contract.

You need to talk to an attorney but I would thank that both renter and landlord wold be covered under the expired contract.

You could be correct, BUT this is Thailand and nothing is that straight forward.

Check the Civil and Comercial Code and or take advice - IIRC it continues on an ad hoc basis for as long as both sides allow it to - therefore there are no effective 'rights' so to speak as either side can end it immediately / or with very sort notice

Month to month on the same terms and conditions.

Month to month on the same terms and conditions.

I agree, that's typically what happens to an expired lease. But again, this is Thailand and things are not quite so "clear-cut".

If the landlord is Thai and you're having problems, forget the legal advice, expenses, etc. Just move out, cut your losses and find another place to live.