We've got a big holiday to Thailand coming up. All flights and hotels already booked but want to make the most of our time while we are there - what's unmissable (or definitely not worth bothering with!). We have a few days in Bangkok, couple of days in Chiangmai, two nights in Phuket and a week on Koh Samui. Me, H, and 2 dds aged 16 and 14; pretty active types. Thanks.