My husband and I are planning a 3 week trip to Thailand over Christmas and New Year. We are looking at spending some time in bangkok, going to Ayutthaya, River Kwai, Chaing Mai and then some time in the South on the beach. We have the first part of the trip pretty well organised (although any tips on accomodation or cookery schools would be great) but it is the beach part we are struggling with. We are looking for somewhere with lovely beaches that are also very peaceful and not very commercialised...does anyone have any recommendations.

Many thanks in advance for any hints and tips!