@Stuart ********
As their parent, you can absolutely be harassed by immigration officers when attempting to leave the country. It happened to me when my son was 6, and a nasty officer kept demanding 10,000 baht cash and tried to prevent us from getting through immigration and onto our plane. If a representative from Bangkok Airways hadn't been standing on the other side of the turnstiles waiting to RUN with us to our gate, I don't know what would have happened. I should also mention that I had my son's completed visa paperwork with me, ready to get his visa from the Thai Embassy in the U.S.