Can I extend 60 Day Visa ?

[gawguy 9]

In the past I was using One Year non OA. Now my situation has changed and I came on a 60 Day Tourist visa. I see a lot of info on line but not sure what is official. So:

Can I extend 60 Day for 7 days? Can I extend 60 Day for 30 days?

I think the 30 day extension would be 1900 baht. How much is 7 day extension.

Thank You,

Gaw Guy