"everything else": car rental and getting from BKK to Krabi directly from ASQ without driver

Hi! I am wondering if it would be possible/relatively hassle free to rent a car and travel down to the south where I will be staying for longer directly without renting a driver through a transfer service... Do I need some certificate to be crossing the provinces as a private person? I would come out of ASQ with a negative test then anyway. Would that be enough? I intend to go in one ride and not stay for a night somewhere. TIA!