By bus[edit]
Buses operate every 20 minutes or so from Bangkok's Northern Bus Terminal (Moh Chit*) directly to Ayutthaya.
First-class air-con buses charge 56 baht. This trip is scheduled to be around an hour and a half,
Also you can take a minivan from the Victory Monument direct to Ayutthaya. Takes ~1 hour and costs 60 baht. Minivans depart every 20 minutes or so.