Do coastal people look down on hillbillies?
Actually, they're looking up. What with the interior having a higher elevation and all.
This isn't a new phenomenon though. Just as Bostonians look down on the hillbillies from the White Mountains of New Hampshire, and Philly residents look down on the appalachian folk of central Pennsylvania, and Potomac River valley residents look down on the hill folk of West Virginia, the coastal peoples of Southern England look down on the Scots. In fact, it's probably the case that the coastal Virginians are of English stock and the West Virginians are of Scottish stock. After all, McCoy and Hatfield are the kind of names you find on Appalachian mailboxes. And all those jokes Virginians tell about West Virginians and their fondness of sheep are probably imported from London as well, who say exactly the same things about the Celts.
So, yeah. At least in the anglophone world, coastal people, fairly or unfairly, tend to be snooty about their urbanity and look upon hill folk as bumpkins. I've noticed a similar attitude in Latin America as well. Perhaps opebo can comment on whether this is also the case among the Thai.