Bangkok to San Francisco by Pan American World Airways

PAN AMERICAN WORLD AIRWAYS released on 30 June 1947 a cover commemorating their first direct airmail flight from Bangkok to San Francisco using a Boeing 314 Clipper. A blue cachet with image of The Grand Royal Palace in Bangkok and Clipper flying overhead highlighted this historic flight. Three Siam (Thi) stamps were affixed to the cover: 15 st - blue/grey coloured stamp of Plowing a Rice Field, 5 st - violet coloured stamp of a young King Ananda Mahidol, and 3 baht - green coloured stamp of  King Rama 7 Prachadhipok. Postmark originated from Bangkok on 30 June 1947;  with reverse side postmark from San Francisco, California.

Pan American World Airways issued a series of covers for the various destinations to promote their routes worldwide. From 1938 till 1948, The Clipper played an active role in their public relations. 

On a side note, the Aviation Safety Award was conferred by Inter-American Safety Council, Inc. for the year 1946 to Pan American World Airways for flying over its 48,440-mile network a total of 43,878,591 flying miles, totaling 760,238,654 passenger miles without an accident or fatality to passengers or crews.

These Siam postage stamps went into circulation well before Pan Am's direct airmail flight.

- Plowing a rice field was issued in 17 April 1941. Quantity: 3,000,000 pieces. Printer: Waterlow & Sons Ltd., England.

- King Ananda Mahidol was issued in 17 April 1941. Quantity: 9,000,000 pieces. Printer: Waterlow & Sons Ltd., England

- King Rama 7 Prachadhipok was issued in 1928. Printer: Waterlow & Sons Ltd., England