This is the largest and most complete museum in Thailand however it doesn't have as many Khmer artifacts as the museum in Phimai. A visit here can be exhausting because there's so much to see. There are several galleries spread out in 14 buildings but most of the Khmer artifacts are located in Building 1 (Gallery of Thai History) and Building 3 (Thai Art History & Archaeology). There are a few well-preserved lintels in both buildings. Building 1 has a very impressive statue of Vishnu with 4 arms. An excellent stone lion sits outside of the entrance to Building 3. Building 3 also has a large horizontal lingam. There's a gift shop next to the ticket booth that has a decent selection of books, including many from River Books. Admission is 200B for foreigners.
Thai National Museum