The headwaters of the river rise south of Double Peak and flows westwards, joined by two minor tributaries; Coondoondoo Creek and Pink Hills Creek.

The Thomas flows through the Murrumburra Pool on its way to the Gascoyne.

The river descends 169 metres (554 ft) over its 127-kilometre (79 mi) course.

[1] Significant gold and tin deposits have been found in the Thomas River Gascoyne gold fields.

This article related to a river in Western Australia is a stub.