It depends on your passport country and what your visa requirements are (if any) to enter Thailand..
If you are from 1 of the 93 countries that now get visa exemption entry then no payment is required unless you apply for a particular visa before travel for longer than your 60 day excemption entry period.
I honestly don't know but I am guessing thier vehicle import regulations are far more relaxed than Thailand because they import all their vehicles simply because they don't have a vehicle manufacturing industry and they drive on the same side of the road as the USA
If you have never been there before then I suggest an extended trip and travel around the country and have a good look