Martin_d ,
just a thought but are any of your AirAsia flights to connect with an international flight back to blightey. We kopped for a delay with them from Krabi to BKK but we were going on to stay in Bangkok for a few days so the delay was a nuisance rather than critical. Looks like you get to use the new airport in BKK and Krabi. Quite a few people were falling foul or AirAsia 15kg hold baggage allowance but they were kind to us allowing out 22kg bags through no bother.
We do need to get a connecting flight, but it doesn't leave Bangkok till 1.30am so we should have plenty of time even with delays. The krabi flight should get us into BKK at 8.10, so worst case scenario we will have plenty of time to explore the new airport!
