If the hustle and bustle and pollution of Bangkok is not for you - head for the sticks! But just remember - you could be miles from civilization and that is not a lot of fun once classes are over and darkness falls. I know three teachers who went to work for Mahasarakham University in the north east. After 6pm, you couldn't get transport into the local town and you couldn't even buy food in the area. They were literally stranded. After 3 months of cycling and fresh air, they yearned for movie theatres and bookshops - and scurried back to big bad Bangers.
Ian says "again it depends on your motivation for coming here and your own personality. If you want to live with the people, be one with the people, learn the lingo & culture and are happy being the only westerner in a 50 km radius then go for it. If you enjoy a McDonalds & a pint of decent beer and chatting with fellow farangs once in a while - think again.