Most of the beach belongs to the resort and occasionally the security chases non guests away but there is a part of the beach that is free to chill at.
Songthaew is a comfortable way to travel between towns.They're cheap, full of locals and cover many routes. Usually they just stop at specific points and passengers pay when getting off.
If I had to choose between this and Marble Mountains, I'd go for this. The way to get there is very nice and you can see beautiful landscapes while from the top on the sunny day you can see whole city.