Chao Sam Phraya National Museum in Ayutthaya
The Chao Sam Phraya National Museum is a rather old fashioned museum, full of dusty display cases stuffed with artifacts. I wouldn't necessarily recommend a visit were it not for the two vaults on the second floor of the main exhibition building. One vault (and I do mean vault, complete with heavy safe doors) displays the gold-and-jeweled goods found in the burial pit at Wat Ratchaburana, while the vault at the other end of the floor has a similar display of items from the shaft of Wat Mahathat.
A bit of trivia: Funding to build the museum was obtained by selling off part of the huge cache of votive tablets found in Wat Ratchaburana. "Chao Sam Phraya" was the given name of King Boromaraja II, who built Wat Ratchaburana.
Between Exhibition Hall 1 and the rather miss-able Hall 2 is an elegant example of a central-Thai styled house. The house is practically a shrine to a past governor of Ayutthaya around the turn of the twentieth century, and is fitted out to appear as it would have been 100 years ago.
There is a fee of 150 Baht (3.90 USD) to the museum. The museum is open from 8:30 am to 4:00 pm from Wednesday to Sunday. The museum is closed on Monday and Tuesday as well as national holidays. You can visit the official Chao Sam Phraya National Museum web site for additional information.