@Josef *******
yes, that will be a problem. Even though your flight shows an earlier return date, your rental shows how long you actually intend to stay, as flights are easily changed, as far as the Thai embassy is concerned concerning your insurance requirement. You will need to be insured as long as your rental contract is valid, as you can theoretically extend your STV visa for a total of 270 days. They do not understand why someone would sign a lease for longer than they intended to stay. That is not logical with as many rentals as are available everywhere.