Thailand. (Horse Shoe Route). 1941. Air Mail envelope addressed to Switzerland bearing SG 297, 1b grey and ultramarine tied by Bangkok date stamp '28th June 84 (41)' with Thai censor circular '6' or '9' in violet, routed via Penang with brown censor tape tied by framed 'Opened By/ Censor. 49' in violet on face and reverse with a red hand-stamp of two parallel bars applied on the printed 'Air Mail' label, censored in London by 'Opened By Examiner 441' label.
Very fine cover paying the 'one baht' rate, carried by B.O.A.C. on the "horse-shoe" routed via Durban, then by ship to Lisbon and air to U.K.. The red parallel hand-stamp indicates the end of air transport.
Morenweiser lists the Penang censor from '2-- 48'.