The national tricolour of Thailand, called thong trai rong, is a horizontal striped banner of the colours red, white, —a slightly broader— blue, white, and red (fig.).

These colours symbolize the nation (red), the monarchy (blue) and religion (white). It was introduced in 1917 by King Rama VI and replaced the thong kha khaay, a briefly used flag consisting of a red field with with two horizontal white stripes (fig.).