Thailand. (Railway Postmarks). 1940. Envelope headed 'The Prince Royal's College, Chiengmai' addressed to New York bearing SG 282, 5s violet and SG 283, 10s carmine tied by bold Chiengmai ambulant railway date stamp '20th May 40' with boxed slogan 'Please use the Telephone and save your time' on reverse with Bangkok transit. Very attractive cover.