I've been to Amanpuri twice and it is one of the finest resorts in the world. You don't need an "ocean view" villa if you can't afford it. The least expensive accommodation is still great. I don't remember the "sand" in Thailand as being memorable. For the best "beach" I would fly from Bangkok to the atoll nation of the Maldives. The beaches there are superb and there are all price ranges for resorts.