Present Thailand a thousand or more years ago. Northern Area of Thailand in many small independent states ruled by kingdom first king Mengrai. 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 under the dominant rule of the Khmer Empire in about the 12th century A.D. The Thai of Center Thailand are named Thai-Noi.