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!

although ko samui is a close second. Try the orchid in KL for peace and seclusion or bang niang for something a little more lively.

Phuket for beaches without a doubt and krabi - what price range for hotels ?
chaing mai try the central dungtawan hotel very nice and well located - can get to your OWN beach in Krabi / Phuket by hiring long tail boat where they will take you to seculded beach / cove with no other access other than by boat - or they also have spectacular populated beaches - avoid surin beach in Phuket too dangerous for swimming although have stayed in surin and its great again depending on price range the twin palms is out of this world and if you e mail me can point to sites with free nights etc etc

and krabi is fun too. why not combine a few things, like phuket or khao lak, then a couple of days jungle/lake adventure in khao sak finishing in krabi for a few days. there are lots of outfits that will pick you up in phuket district, organise jungle adventures for a few days (you can even stay in a tree house or luxury tent if you want- try elephant hills) and drop you off in krabi instead of returning you to phuket.

Thanks very much for these. I will look into the centara in chiang mai.
Given the time of year we are going, do you think that it is best to book all of our accomodation and activities in advance? If so, do you recommend any companies or is it best to book hotels direct?

We used agoda for the centara and booked direct with most others, it depends who is offering what prices and packages! I think any overnight adventures might be best booked in advance (have a look at siam safari, limestone lake tours and elephant hills websites, for example), but day trips can easily be organised a day or two beforehand, either in your hotel or at the many many tour places around all your destinations. You do need to do a little price comparison- flight of the gibbon was cheapest booked via the centara tour desk but other things were more expensive. We also booked our cooking school before we left home, but this wasn't really necessary.

My husband is taking a sabbatical next january and will be in thailand for his 60 days, sadly, I can only join him for 2 weeks or so, but will make the most of it!

Should be calm at the time of year you are going.