you cannot get marriage visa without proof of legally married to a Thai woman. If you visit Thailand to marry her, you cannot get non-O before your marriage.
Just unnecessary additional info as many people are mixing up visa validity and entry stamp.
As Lloyd said, the visa itself's validity of 90 days (<- the period you can use that visa to enter Thailand to get an entry stamp for the status on the visa) starts on the issued date but the Thai embassy/consulate.
Your 90-day stay on Non-O starts on the day you enter Thailand within the visa validity as day 1, even if you enter Thailand on the last day of visa validity.
CW office accepts bank letters up to 7 days old (including the issued date). Get the letter and transaction in advance.
You can update your bankbook anytime on the day after midnight. You can deposit/withdraw and update your bankbook on ATM/CDM/PUMs before the branch opens.
There are copy shops one floor under and they are open before 8:30.