The first flag of Thailand was a simple red one and was used for Siam under king Narai (1656-1688).Various symbols were however used in the naval flags like a white chakra known as the Buddhist Wheel, a white elephant inside the chakra or a white disc with sun inside. In 1855 the first national flag of Thailand was accepted by king Mongkut.
The Thailand flag had a white elephant on red ground. The elephant is considered as the national symbol. This was done because the earlier flag was not clearly visible while representing international relations. In 1917 the color of the middle portion was changed to blue. Blue is the color of Friday, which is also the birthday of Vajiravudh, the king of flood. The flag of Thailand very well resembles the flag of Costa Rica. The only difference is that the blue and the red colors are inverted.
