How far south can I travel by bus or car, without the need to take any boat/cruise and without any permits?
Lonely Planet Myanmar (print edition, Aug 1 2014) says:
But briefly Googling, I find one November 2013 forum post that slightly contradicts the above, stating that you can get as far as Myeik by bus:
The 2013/14 summer is the first time in 50 years that overland travel on along this lush coast has been permitted. Here is how to get there....by intercity bus, flight, train or boat.
Before you ask, unfortunately the Mergui Islands are still restricted to those with prior permission from Nay Pyi Daw (as at Nov 13), but the mainland has plenty of history, culture and barely discovered beaches for the adventurous to enjoy. Maung Ma Kan, Nebule, Myawyik Island, She Moe, Palaw beaches just to name a few