Thailand. (Air Mail). 1924. Air Mail envelope addressed to Bangkok bearing SG 213, 3s red-brown (pair) tied by small 'aeroplane' date stamp of UBOL dated '9th Dec 1924' with Bangkok arrival on reverse '12.12.24'
Carried on the weekly flight of the Royal Aeronautical Service from Ubol (Ubon Ratchathani) to Bangkok.