Would it be best to go to Ayuttaya for a day trip from BangKok? I also want to go to Chiang Mai - could take the train from Bangkok or go back to Bangkok from Ayuttaya and fly to Chiang Mai - Thanks
For Ayuttaya from Bangkok, a day trip by bus and boat is a good option. Will be a longish day but certainly doable. Lots of tours available from Bangkok. However presently Thailand is suffering from major flooding and this area is badly affected.
To Chiang Mai - best to fly - quick and reasonably inexpensive. My choice would be Thai Air since Air Asia is a low cost airline and will charge for all the extras like baggage. Their std checked in bag limit is 15 Kgs and their allowance for cabin bag is very very small. They will then charge a large amount for excess baggage. In the end I have found Thai Air to be only slightly more expensive.