For one reason or another I am thinking about extending my Non Imm Married visa renewal from Satuday to Monday which will make me two days past the required date. While I am willing to pay the 400 baht this will cost as a penulty would I possibly lose this visa altogether if I am past the required extension date?

Probably not, but don't take my words as truth.  You should call the people at Immigration and tell them why you can't come on time, and get the name of the official, just to be sure.  There's too many changes going on now from day to day to trust past experience.

If you go on overstay they can get a little funny (I was on overstay and should've been entitled to a 10 day extension...they gave me 3 days) about it, best, as chappie above says, to contact them first. The last thing you want to do is start all over again!