Ko Samet, Ko Chang, Pattaya, Rayong- basically beach places of varying beauty and development. You can go on to Aranyaprathet-Poi Pet which is the border.
Hello. Bkk and Pattaya got Simi to offer?
Both got **** ton of people and tourist. So boring.
Then u think Sa Kaeo and Chon Bu Ri got a lot to offer? Yes you won't see tourist there, but you won't see anything else too. If you just want to get disconnected from the world, that part of Thailand is not suitable for it. If you just want to see ancient temples, go Phitsanulok and Sukhothai.