Thailand. (New Zealand - Printed Matter Rate). 1940. Envelope addressed to New Zealand bearing SG 286, 3s green tied by bilingual Bangkok/ 4 date stamp '13th March 40', routed via Singapore with triangular 'Passed For Transmission/ 13' on face and hand-stamp arrival '12th April 1940' on reverse.
Nice item paying the unopened Printed Matter rate from Siam to New Zealand via Singapore.