The names Shan and A-hom seem to be variants of the same word. The word Śyâma is possibly not its origin, but a learned and artificial distortion. Another theory is the name derives from the Chinese calling this region 'Xian' A further possibility is that Mon-speaking peoples migrating south called themselves syem as do the autochthonous Mon-Khmer-speaking inhabitants of the Malay Peninsula. The signature of King Mongkut (r. 1851–1868) reads SPPM (Somdet Phra Poramenthra Maha) Mongkut Rex Siamensium (Mongkut, King of the Siamese). This usage of the name in the country's first international treaty gave the name Siam official status, until 24 June 1939 when it was changed to "Thailand". Thailand was briefly renamed Siam from 1946 to 1948, after which it again reverted to "Thailand". History Prehistory There is evidence of continuous human habitation in present-day Thailand from 20,000 years ago to the present day. The earliest evidence of rice growing is dated at 2,000 BCE. Bronze appeared circa 1,250–1,000 BCE. The site of Ban Chiang in northeast Thailand currently ranks as the earliest known centre of copper and bronze production in Southeast Asia. Iron appeared around 500 BCE. The Kingdom of Funan was the first and most powerful Southeast Asian kingdom at the time (2nd century BCE). The Mon people established the principalities of Dvaravati and Kingdom of Hariphunchai in the 6th century. The Khmer people established the Khmer empire, centred in Angkor, in the 9th century. Tambralinga, a Malay state controlling trade through the Malacca Strait, rose in the 10th century. The Indochina peninsula was heavily influenced by the culture and religions of India from the time of the Kingdom of Funan to that of the Khmer Empire. The Thai people are of the Tai ethnic group, characterised by common linguistic roots. Chinese chronicles first mention the Tai peoples in the 6th century BCE. While there are many assumptions regarding the origin of Tai peoples, David K. Wyatt, a historian of Thailand, argued that their ancestors which at the present inhabit Laos, Thailand, Myanmar, India, and China came from the Điện Biên Phủ area between the 5th and the 8th century. Thai people began migrating into present-day Thailand around the 11th century, which Mon and Khmer people occupied at the time. Thus Thai culture was influenced by Indian, Mon, and Khmer cultures. According to French historian George Cœdès, "The Thai first enter history of Farther India in