Thailand forum

If you know your dates I'd look at booking asap as prices will only rise over the busy Christmas period. If you want to fly directly from Bangkok to Ko Samui you're limited to Bangkok Airways who have a monopoly on flights there. Their own website will probably give you as good a price as any.

If budget is more important consider flying to Surat Thani (or even an overnight bus) and catching a ferry, particularly if Ko Phangan is your destination as you can go directly there from Surat Thani. Air Asia are generally a good bet for Surat Thani flights but check out Skyscanner for a comparison of what's around.

Well, I suspect you'll still be able to pick up a fairly cheap Air Asia flight to Krabi a lot cheaper than the fare to Ko Samui ........ As for the train, I guess it depends a lot on how old the kids are. I have no experience of travelling with kids but I was on a train a bit back with a couple who had 2 young kids. They had an upper and a lower berth and their plan was for each of them to have one of the kids in the berth with them but they were not comfortable with having a small child in the top bunk; with the swaying of the train they were worried they might fall out (the top berths are also a bit narrower than the lower ones). Again, depends on their ages but may be something to consider.

cocopops,

i don't think the train goes to krabi, so you'd need to get off at surat thani or trang or nakhon si thammarat and bus it from there to krabi. if you do decide to take the train, look into booking two adjacent first-class compartments that have a door that opens between them. we did this with friends once on the trang-bangkok sleeper train run and it was great fun and should be a great adventure for you and the kids.

whatever you decide, train or flights, i'd book as soon as your dates are set, as the international new year is a busy travel time in thailand. good luck.