Thailand. (Laotian Civil War). 1971. Stamp-less Air Mail envelope addressed to Bangkok cancelled by Pua date stamp '22nd Sept 2514 (1971) with 'Royal Thai Army Border Patrol/ Command' hand-stamp in violet/ blue on face, endorsed 'Army Censor/ Checked' and signed by the Commanding Officer and Bangkok '24th Sept' arrival on reverse.
Royal Thai Army Troops had been in the Doi Phu Kha, National Park (Nan Province) on the Thai Laos border as part of 'Operation Phalat' a military offensive of the Laotion Civil War.