I see three bugs, are they multiplying.
Didn't start photography in Vietnam ,but did get my first SLR there. A Minolta SRT 101. Also several lenses . I was in a Army bridge company so I was driving a 5 ton dump and had room for a lot of equipment in he cab. Shot mostly slide film them.
#13: Is probably coal fired, The cylindrical tank is for water, the stack on the engine suggests coal fired
As a "train nut" as well as a photographer, the last picture bothers me. It is never safe to be between the rails