Practical information about Ayutthaya Floating Market
You can go around market by boat for 20 THB. The pier is opposite of the brick wall near the beginning of the market. Adjacent to Ayutthaya FLoating Market is the Intermarket Ayutthaya, on land this time. It offers other shops and possible elephant rides in the ruins of a temple behind (no really interesting, there are so many other ways to spend time with elephants in more pleasant fo conditions for them in Thailand, but it exists).
To go visit Ayutthaya Floating Market, you can also book one of the tours above.