I have a US passport that is almost full and I'd like to make one last visa run to Vientiane using it (to get a Single-Entry Tourist Visa). I have two pages left that are totally empty, which I will need to use for the Laos visa and the SETV visa (each of which takes up a full page of my passport). I have two other pages that already have some stamps on them but have some empty spots. Can I assume that the immigration officers (both Thai and Lao) will put their stamps on the pages that already have stamps on them, so that the two totally-empty pages will be available for the visas?