Further south, in which is now central Thailand in the Menam valley or Chao Phya basin, there were evidently some settlements of the Thai people. At first they were minority groups, which probably later on, formed themselves into semi-independent principalities under the dominant rule of the Khmer Empire in about the 12th century A.D. the Thai of central Thailand are named Thai-Noi or Minor Thai in contradistinction to the Shans of Upper Burma who are named Tai Long or Thai-Yai i.e. Major Thai. It is a traditional belief that the Thai-Noi or Minor Thai of Central Thailand came from the Thai of Northern Thailand and the Lao kingdom. this may be so but on the other hand there are indication that the Shans of Upper Burma might have had a share, if not much in Making up the ingredients of the Thai-Noi too.
There arose in the earlier part of the 13th century A.D. two chiefs of the Thai-Noi who wrested from the Khmers the area of central Thailand and one of them became the first Thai king of Sukhodaya, a town some 150 kilometers as the crow- flies north-ward from Bangkok. Under the reign of its third king, Ram Kamhang the Great, contemporary and friend of the aforesaid Thai King Mengrai of Northern Thailand , the kingdom of Sukhodaya became a relatively large empire stretching southward through the length of the Malay Peninsula which was the last remnant of the once Javanese Sumatran Empire of Sri Vijaya. Northward, the Sukhodaya Empire youched that of northern Thailand where reigned, as already mentioned King Mengrai. Eastward but in northerly direction, through what is now the North-East Area of Thailand which was at the time partly under the spheres of influence of the now decaying Khmer Empire and of the Lao kingdom, the Sukhodaya Empire of King Ram Kamhang reached further beyond the river Mekong. Westward it included a part of the Mon country of what is now Lower Burma. Ram Kamhang’s outstanding achievements in the realm of culture which have endured to the present day are his invention of the Thai alphabet in 1283 A.D., and the adoption of Buddhism of they Ceylonese Sect which has remained to this day. He also introduced the manufacture of glazed pottery by importing artisans,no doubt from China.