Roundel of the Royal Thai Air Force (1941-1945)
In December 1941, after the occupation of Thailand by Japan (after Thailand formally joined with the Axis powers), the RTAF changed the roundel again to avoid confusion with the British RAF roundel. The "running Elephant" is a version of the former Flag of Siam before the  November 28 1917.

The RTN (Royal Thai Navy), however insisted on still using the 1919 roundel throughout the war.
Based on aviation of japanRTAF history, warthunder.ru
Sodacan