You can extend for 7 days but you gonna pay 500 everyday of overstay. If they give you even 7 days extension, you can transfer your visa to another passport. I just did it this year but was not late as you.
But you will be ok, just will have to pay overstay. Go go!
They do at Surat Thani for 3000thb till 31st January, no need to come again. If you pay 1900, you need 2 copies of everything and come again in 2 weeks getting your second stamp( can be done in Samui)