Tomorrow is the annual Trat remembrance day (วันตราดรำลึก), as on March 23 1906 the province Trat was returned to Thai suzerainty after being held captive by the French since 1904. The most remarkable thing about this celebration is that on this day the whole province uses the old flag with the white elephant on a red cloth. This flag was abandoned in 1916, allegedly because the king saw this flag hanging upside down after a flood, and then changed the national flag into a symmetrical one which cannot be hung wrongly. At first the middle bar was red as well, after one year it got the blue color it still has today.
I have found a collection of photos from the Trat day 2007 which show perfectly well that on this day the old flag is much more present than the current national flag. The above illustration is taken from Le Petit Journal of February 26 1905 and shows the occupation of Trat by the French. So instead of the reraising of the elephant flag in 1906 it actually shows the earlier lowering. Trat was given to the French in 1904 in exchange with Chanthaburi, which they occupied in the Paknam crisis of 1893. And though Trat celebrates March 23, for nationalists it would be more a day of mourning, as with the contract which returned Trat the northwestern provinces of Cambodia had to be seized to French Indochina.