If you have time enough (one week), I would be happy to organise for you a trip by car from Siemreap to visit the temples and cities in the regions belonging to the Khmer empire but now located in Thailand and far from the beaten track in that country.

Other Museums in the world

Musée Guimet in Paris (France)
www.museeguimet.fr

The South East Asia Department was a result of a merger between two major collections of Khmer art, between 1927 and 1931: the old Musée Emile Guimet collection -with the series of Cambodian artefacts built up by Etienne Aymonier (1844-1929)- and the collection of the Trocadéro Musée Indochinois of which Louis Delaporte (1842-1925) had been the founder and curator. Up until 1936, these collections were supplemented by material sent by the Ecole française d'Extrême-Orient, including the Banteay Srei pediment (MG 18193). The range of Khmer sculptures provides an illustration of Cambodian art from its origins up to the present day, and is unique in the West. It reflects the French contribution to knowledge of this prestigious civilization.
While the section devoted to the arts of South East Asia is particularly rich in material from Cambodia and Indianized Vietnam (Champa) it also features a selection of works which provide a panoramic display of the arts of Thailand, Indonesia, Sinicized Vietnam, as well as Burma and Laos.