It is easy to visit Ayutthaya on a day trip from Bangkok. The tours offered by local agencies or guides bring you to the main temples of the historical city listed as a UNESCO World Heritage Site. Sometimes, they also make a short detour to Bang Pa-In to visit the royal palace and the atypical Wat Niwet temple or go to Wat Muang in Ang Thong to respect the tallest Buddha in Thailand.
Of course, you can decide to extend the experience and not return to Bangkok in the end of the tour.
You can book a hotel in Ayutthaya here.