Tod Daniels wrote this. to get 9 months out of a 6 month METV you get the visa as close to the time you're coming here as you can (because it's valid for 6 months from the date it's issued)
You arrive get stamped in for 60 days
when that runs out you go to the border, stamp out/in get 60 more days
when that runs out you go to the border, stamp out/in get 60 more days
when the VISA itself is almost expiring you go to the border stamp out/in and get a final 60 days (taking you to almost 8 months)
Then you extend that last entry by 30 days at the immigration office for 1900baht taking you to 9 months total