Flags of Thailand

Kingdom of Thailand (constitutional monarchy)

Who & why: a bloodless coup by the People's Party on 24 June 1932 forces King Prajadhipok to accept a constitution, ending absolute monarchy and installing a constitutional system under which the Chakri dynasty continues to reign, now as head of state rather than sole ruler. The country renames itself from Siam to Thailand in 1939, and remains, into the twenty-first century, the region's only country that never fell under direct European colonial rule.

What it represents: the trirang of 1917 continues; Wikipedia says the Flag Act of 1979 (B.E. 2522) set the proportions at 6:9 with the blue middle band two parts wide, and that the Office of the Prime Minister standardised the colours using CIELAB values on 30 September 2017. Blue is unofficially read as the monarchy, white as religion and red as the land and people.

Kingdom of Siam (late absolute monarchy)

Who & why: King Vajiravudh (Rama VI) adopts the red-white-blue trirang in 1917, adding blue in solidarity with the Allied powers of World War I, into which Siam enters that same year — a modernizing, internationally minded gesture from a monarchy still ruling by decree.

What it represents: five horizontal bands, the middle one changed from red to dark blue on 28 September 1917 to give the current design, with the Flag Act of 1917 making it the national flag. Explanations for blue include solidarity with the Allies in World War I and the auspicious colour of Vajiravudh's birthday (a Saturday); red is read unofficially as the nation, white as religion and blue as the monarchy.

Kingdom of Siam (Chakri dynasty, absolute monarchy)

Who & why: General Chakri founds the still-reigning Chakri dynasty in 1782, crowned Rama I, and moves the capital across the river to Bangkok. Across the nineteenth century, Kings Mongkut (Rama IV) and Chulalongkorn (Rama V) pursue deliberate modernization and adept diplomacy between British and French colonial ambitions, ceding some peripheral territory to each but preserving the kingdom's core independence — the singular achievement that sets Siam apart from every neighboring state.

What it represents: Wikipedia says Rama I decreed a red flag with a white chakra around 1782, Rama II added a white elephant inside it around 1817, and Mongkut (Rama IV) made the white elephant on red the official flag in 1855 because the plain red flag was not distinctive enough for international use. In 1916 Vajiravudh introduced a state flag with the elephant in royal regalia, followed by a red and white five-stripe flag in 1916–17. The plain red flag therefore preceded the elephant rather than being gained under Rama II as the ship ensign.

Sukhothai and Ayutthaya kingdoms

Who & why: the Sukhothai kingdom, traditionally dated from around 1238, is often regarded as the first unified Thai state and the origin of the Thai script under King Ramkhamhaeng; it is absorbed by the rising Ayutthaya kingdom, founded in 1351, which dominates the region as a major trading power for over four centuries. Ayutthaya falls to a Burmese invasion in 1767, and a brief Thonburi kingdom under Taksin bridges the gap until General Chakri founds the modern dynasty in 1782.

What it represents: Wikipedia says Siam used a plain red flag from about 1680 to 1782, probably first under King Narai (1656–88). It does not cover Sukhothai, so no earlier flag is claimed.

Dvaravati and Khmer-influenced Mon kingdoms

Who & why: centuries before Sukhothai's traditional 1238 founding, the Chao Phraya basin is home to Dvaravati, a loose network of Mon-speaking Buddhist city-states known mainly through inscriptions, coinage, and distinctive dharmacakra stone monuments rather than a unified political history. By the 11th–12th centuries the expanding Khmer Empire, ruling from Angkor, extends its own overlordship over much of this territory; Sukhothai's founding in 1238 is traditionally remembered as a local uprising against that Khmer authority, the event that opens the entry which follows. Deeper still, archaeological sites like Ban Chiang in the northeast attest to a sophisticated Bronze Age culture in the region dating back to roughly 1500 BCE, among the earliest known in Southeast Asia, though it left no continuous political history connecting it to Dvaravati.

What it represents: no flag or comparable unifying banner is documented for either the Dvaravati city-states or the Khmer administration of the region; shown here honestly blank rather than invented.

World context: the height of Khmer overlordship over this region overlaps with the Khmer Empire's own construction of Angkor Wat in the early 12th century, one of the largest religious monuments ever built, as well as the Song dynasty's flourishing in China and the Chola Empire's naval expansion across the Bay of Bengal — and, at the deep end of this entry's span, Ban Chiang's Bronze Age metalworking was already contemporary with the mature Shang dynasty in China.