For the TM7 extension, what is the required size of the photo and what do they mean by 'affix' exactly, tape? TIA

Wanting sanity check on this. My US obtained METV (valid until Oct 31) and my last METV border bounce got me admitted until Dec 25, 2018. My CM approved TM7 extension takes me to January 25 2019. I believe a second CM TM7 30 day request will result in a denial with 7 days to vacate? So – to get 60 more days I’m thinking Vientaine for SETV (20,000 bht, proof of onward travel and accommodations) or just a visa run to Mae Sai for 30 day new visa exempt stamp ? Also if I do the Mae Sai option for a new 30 day visa exempt does the new 30 days start immediately upon entry into thailand or does it tack onto the TM7 extension?