Siamodon is known from the holotype PRC-4, a well-preserved left maxilla and from the referred materials PRC-5, an isolated maxillary tooth and PRC-6, a braincase. It was collected in the Ban Saphan Hin site, Nakhon Ratchasima Province, from the Khok Kruat Formation, dating to the Aptian stage of the late Early Cretaceous, about 125-112 million years ago.