Mengrai at the centre. The kings of Lanna (Mengrai) Ngam Muang (Phayao) and Ram Khamhaeng (Sukhothai).
"In 1280, Mangrai first made peace between King Ngam Muang of Phayao and King Ram Khamhaeng of Sukhothai, who had seduced the former's queen. The three Kings then entered a pact to defend their lands against the expanding Mongol Empire." Wikipedia http://en.wikipedia.org/wiki/Mangrai