I've read that the trains coming through Ayutthaya to Bangkok can sometimes get delayed, so I'm nervous about whether or not it's a reliable option for someone needing to get to the airport.
At that time of the morning, everything is delayed.
because we are talking expensive flights, I would have a taxi / private ride arranged in Ayutthaya. Public transportation has too many chance for failure.
You could take a van to Victory Monument (around 1 hour) and then change to either another van to the airport from in front of the Fashion Mall at Victory Monument, or take the BTS one stop to Phaya Thai and then the ARL train.
This should be doable as long as you start out early enough. I would try to be at the airport three hours before your flight.
But there's a lot of wisdom (and certainly more convenience) in OctoberSix's solution.
As mentioned by Octobersix I would have a private car / taxi booked.
Oh, and the trains are NOT reliable. Don't even think of using one in this situation.
Thanks for the advice, everyone!
The taxi option may win out, seeing as we'll have all our luggage, too.
I appreciate the feedback!
How do you book a taxi in Ayutthaya?
When I asked the same question on here a few months ago I got told there weren't any based in Ayutthaya, and racking my shell-like I can't remember seeing any when we were there last month. Loads of tuk-tuks but no taxis!
You ask the desk at your hotel to book a private transfer. Or use the internet to book yourself (with Oriental Escapes for example).