There are now two floating markets in the old city of Ayutthaya which make a nice change from just visiting old temple ruins all day. Now you can break up your time to make a more balanced day trip from Bangkok. Earlier I visited Ayutthaya Klong Sa Bua Floating Market which is to the north of the old city. The next one that I visited is to the East [MAP] and goes by a similar name, though they use different spelling. This one is Ayothaya Floating Market. It is conveniently next door to the Elephant Camp so you can do an elephant ride for 600 baht if you like before visiting the market.
The two floating markets in Ayutthaya are very different. This one is more traditional and what you would expect to see at a floating market. Like the Pattaya Floating Market, it is purpose built. It is free to enter and wander around. There are shops with handicraft and souvenirs. Nothing tacky like the ones you can find at Damnoen Saduak Floating Market. If you want to eat then there are plenty of stalls selling delicious food. You can also take a boat ride around the canal for only 20 baht.
You can easily spend a couple of hours at this floating market. As well as shopping and eating, there are also regular shows during the day. These include boat parades as well as traditional dancing at various arenas around the market. We were there at the weekend and it was very crowded with coach tours and Thai tourists. If you want to escape the crowds then come during the week though the shows are not so regular. Parking is also a problem at the weekend.
If you are visiting Ayutthaya for the day from Bangkok then there is really only time to visit one of these floating markets, do an elephant ride and visit 3 or 4 temple ruins. If you want to visit both floating markets then I would suggest that you stay over night. I enjoyed myself at this market and would certainly bring friends here on my next trip. The market is open every day from 10 a.m. to 9 p.m. Weekday shows are 12 p.m., 5 p.m. and 7 p.m. At the weekend it is 10:30 a.m., 12 p.m., 2 p.m., 4:30 p.m. and 7 p.m.