This point is worth noting.

The names of kings of Suhhothai also suggest a change in culture or bloodline.

ขุน บานเมือง -- Thai name

ขุน รามคำแหง -- Pali name (rama- ka-amha.m ; rama: likeable, ka: who/that, amha.m: powerful)

may co-incide with the rise of Theravada Buddism in Sukhothai.