Update: I am back from my Visa run to get a Multiple entry Non-Im O visa at Saigon.
Required documents: Passport, letter from wife, Marriage Certificate (Photocopied front and back), Blue Book, Wifes I'd card signed. That's all they ask for on the website.
Only problem was once he went through everything. He wanted to see a print out of my finances. Luckily I had my Bangkok Bank passbook with me that I had updated the week before.
He went through every page. I did say do I need that since I have to leave every 90 days. He didn't answer and sent me off to get every page of the passbook photocopied. (Not a problem as there is a shop about 100 meters away.)
Apart from that everything went smooth.