Thailand’s current national flag has five horizontal bands: red, white, dark blue, white, red. Its hoist-to-fly ratio is 2:3, and the central blue band is twice as tall as each other band. The tricolor was adopted on 28 September 1917.
Specification
Section 5(1) of the 1979 Flag Act prescribes a rectangle six parts high and nine parts long. The dark-blue middle occupies two parts of the hoist; each white and red band occupies one part. The Act also names it Thong Trairong, the tricolor. This record covers the plain national flag; the naval ensign is separately defined in §5(2).
Physical color reference
NSTDA’s account of the 2017 Office of the Prime Minister guidance gives these recommended cloth color measurements under CIELAB, illuminant D65, with ΔE* no greater than 1.5 for each color. These are official recommendations, distinct from the Act’s named colors.
| Color | L* | a* | b* | ΔE* limit |
|---|---|---|---|---|
| Red | 36.4 | 55.47 | 25.42 | ≤1.5 |
| White | 96.61 | −0.15 | −1.48 | ≤1.5 |
| Dark blue | 18.63 | 7.89 | −19.45 | ≤1.5 |
Screen specimen
The SVG uses the HEX values also displayed on the Thailand government portal. They reproduce colors on screens; they do not replace cloth measurement or certify a manufactured flag.
#A51931 / screen reference#F4F5F8 / screen reference#2D2A4A / screen referenceConstruction notes
On a nine-unit fly and six-unit hoist, place horizontal boundaries one, two, four, and five units below the upper edge. Every band spans the full fly. This construction follows directly from §5(1); it produces matching upper and lower halves, with no added symbol, border, or canton.
The specimen has a 900 × 600 viewBox. A red rectangle fills it; a white rectangle from y=100 to 500 and a blue rectangle from y=200 to 400 produce visible band heights of 100, 100, 200, 100, and 100. This is a scale rendering of the legal geometry, not a sewing pattern: hems, sleeves, seams, and textile testing require production guidance beyond these proportions.
Meaning and use
The Public Relations Department’s National Flag Day account explains red as the nation and its people, white as religion, and blue as the monarch. These meanings are government explanatory guidance; §5(1) specifies the design without defining its symbolism. The same account documents official flag ceremonies and the annual 28 September observance, first held in 2017. The flag represents the country in national and public display.
Historical record
The present tricolor dates to 28 September 1917 under King Vajiravudh (Rama VI), when the country was known as Siam. It remains the national design. Flags of the World records the change of the central stripe from red to blue in 1917; that earlier red-and-white design is a predecessor, not an alternative current specimen.
The current statutory description comes from the Flag Act B.E. 2522: given on 22 April 1979, published on 30 April, and effective the following day under §2. This later legislation restated the flag rather than introducing the tricolor in 1979. The 2017 color recommendations likewise refine reproduction rather than establish a new five-band design.
Source distinctions
The government portal’s brief history mixes 1916 with the 1917 Act and refers to the 1936 law as still in use. For chronology this record follows the PRD anniversary account and the vexillological reference; for legal specification it follows the 1979 Act, whose §3 repeals the 1936 Act. The original Gazette PDFs could not be retrieved during review: the Act was checked through its Thai transcription and corroborating references, and the physical color table through NSTDA. Detailed textile measurement conditions beyond D65 and the reported tolerance have not been independently checked here.
Source trail
- Flag Act B.E. 2522 (1979), Thai transcription: §§2–3 and 5(1); publication note identifies Royal Gazette volume 96, special part 67, page 1, 30 April 1979. Original Gazette locator (unavailable during review).
- National Science and Technology Development Agency: Thai flag color standard: measured cloth values, D65, tolerance, and advisory status. 2017 Prime Minister’s Office announcement, Gazette locator (unavailable during review).
- Thailand government portal: The flag of Thailand: proportions, names, meanings, and display HEX values; historical inconsistencies noted above.
- Public Relations Department, 27 September 2024: 107th adoption anniversary, color meanings, and National Flag Day use.
- Flags of the World: Thailand: corroborating 1917 history and §5(1) geometry.
- Wikimedia Commons: Flag of Thailand.svg: inspected SVG code, Zscout370 and contributor history, and public-domain declarations. Local asset and rights record.
Related records: Singapore · Vietnam · National flags.