What are the requirements for a non-immigrant O visa extension in Thailand?

I got my non-imm O Thai wife extension confirmed this morning, a huge thank you to everyone for the advice in getting it done.

One point from today - if like me you have a pile of visa size photos sitting in a draw, be careful. I've used the same batch in the past, but this time they had last year's application out and made me go and have a new photo taken. They said the photo must be less than 6 months old. Not a massive problem, I got it done in the basement for B100