Just an FYI in case it’s of use to anyone (as I wasn’t sure if I’d get any problems) - Following the expiration of my METV I went to Mae Sai and got a 30 day visa exemption no problem, no questions asked. I’d also done all of my border bounces there to activate the 60 Day stamps throughout the METV (and had got the 9 months out of the METV).