What are the requirements and fees for extending a METV in Thailand?

Yes fees... yes papers... yes wait in line

You get a 60 day stamp every time you enter thailand.

enter the first time 60 days

enter the second time 60 days

enter the 3 time 60 days

enter once again just before the "enter before" date on the VISA 60 days

extend that by 30 days

Total almost 270 days IF you time the bounces right and make sure you do the final one just before the enter before date on the visa itself

The way you get the most out of a 6 month METV is first get it very close to the time you are comin' to thailand. So you don't burn down the validity of the visa not being here :/

You come in get a 60 day stamp. When thats running out you border-bounce <- go to the border, stamp out of thailand stamp in&out of another country and stamp back into thailand to get another 60 day stamp

when that runs out you border bounce again to get another 60 day stamp.

THEN just before the "enter before" date on the VISA itself you bounce once more getting the last 60 day stamp (taking you to about 240 days) and you extend that last stamp by 30 days for 1900baht taking you to 270 days or almost 9 months on that visa.

There is no way to get more than about 9 months out of that visa.

Maybe take your proof of residency here as well together with photo and copy of your passport including visa stamps.

You are mistaken. IF you are applying for a 30 day extension of stay there is a 1900baht fee and the required paperwork.

With the METV you either exit/re-enter the country to get another 60 day stamp OR you can extend your current stamp by 30 days for 1900baht and then when that winds down you exit/re-enter the country to get another 60 day stamp.

A 6 month METV doesn't meant you can stay inside the country for 6 months. It means the visa is valid for unlimited 60 day entries during the 6 months