Phayao legend began with one lord titled Khun Chom Tham, son of Phaya Lao Ngoen Rueang, ruler of the Hiran Ngoenyang Kingdom.

Lao Sin became the new ruler of Hiran Ngoenyang while Khun Chom Tham gathered an army and citizens to build a new territory.

At the age of 25, Khun Chom Tham brought his troops down to Chiang Muan area.

In the myth, Khun Chom Tham found a deserted town at the end of the Mountain Range.

Phayao was cited in the wider campaign of Mangrai to consolidate Thai territories, which was driven by two factors: the neighboring kingdoms' slight to his authority; and, the scarcity of space and resources for the growing population of his subjects.