Can I leave Thailand multiple times on a METV and still get 9 months of stay?

This looks interesting, what is metv?

Yes you can enter/exit thailand as much as you want for the validity of the visa itself (6 months from the date it's issued) and you'll get stamped in for 60 days every time you enter.

Now whether you get 9 months out of it or not totally dependent on you. You need to exit/re-enter thailand just before the "enter before" date stamped on the visa itself which gives you another 60 days and then extend that entry by 30 days at the immigration office for 1900baht.