Here's another one with a different dog! This one was on the BTS with us getting off at Phrom Phong.
I can see his "Special Branch" (191/RTP) keystone patch. My guess was this was for show on Children's Day and not due to "political" issues. ISOC (RTA) and the Junta have tens of thousands embedded and monitoring the "political situation".
But that's just a guess as I didn't see anything similar on dozens of lengthy BTS and MRT trips over the weekend, before and after. The Special Branch guys usually move in teams of two, during times of duress.