By the beginning of the 19th century (B.E.),
Pho Khun Ban Muang, the 1st son of
Sri Indraditya and his younger brother: Ram Khamhaeng expanded the Sukhothai kingdom.
making Sukhothai controlled most of present-day Thailand. (Only the eastern provinces remained under Khmer control.)
To the south, Ramkamhaeng subjugated
the kingdom of Supannabhum and Sri Thamnakorn (Tambralinga) and, through Tambralinga, adopted Theravada as state religion.
To the north, Ramkamhaeng put Phrae and Luang Prabang (now in Laos) under tribute.