You will need Copy passport photo page, copy visa page/ stamp, 2 passport sized photos, 1900 baht for 30 day extension. You can get the form you need to fill out at immigration.
you can extend at the end of the 90 days for a further 2 months, but some immigration offices will only do it once, so i would go ask at your local immigration office. Are you going to teach in thailand?
go to savannakhet laos with the correct paper work, pay the 5000 baht fee, come back to thailand. You get 1 year, but u must go out of thailand every 90 days. U wont be refused entry with that visa.
I thought you had to keep the money in the bank until you actually get the 1 year extension, then 3 months after that for a check up. Or is it not the case. Saying that every immigration office is different.