Thai people, who originally lived in southwestern China, migrated into mainland Southeast Asia over a period of many centuries. The oldest known mention of their existence in the region by the exonym Siamese is in a 12th-century inscription at the Khmer temple complex of Angkor Wat in Cambodia, which refers to syam, or "dark brown", people. It was believed that Siam derived from Sanskrit syama or "brown (people)" with a contemptuous signification. was the name for the northern kingdom centred on Sukhothai and Sawankhalok, but to the Thai themselves, the name of the country has always been Mueang Thai.