I served in the Northeast. I taught English at Nangrong School, which is not anywhere near the waterfall of the same name. It's in Amphur Nangrong, in Buriram province (a little ways past Korat, before you get to Surin and Srisaket), on the Cambodian border. I was in Group 10 -- 1965 to 67.
I'll be interested in hearing more about the Friends of Thailand group, and I'll probably want to join. I seem to remember that there used to be such a group -- back around the time of the celebration of the 25th anniversary of PC -- but I guess it died. I have a vague memory of eating Thai food with them on the steps of the Lincoln Memorial, although I was never a member. (I was there for the 25th anniversary celebration, and they had their Thai dinner during that event.)