I shows you are still married and your marriage still appears on the register. You can get it at your local Amphur for 20 Baht. Best issued on the day or the day before your visit to immigration.
As to needing it at the office you use, I have no idea, but as you have such a long travel, if it were me I would be taking it with me.
in the past, I have ordered a 1 year statement about 6 weeks before my renewal, it took about a week to get it, as the local branch (Buriram, Bangkok Bank) said it had to come from Head Office.
On the day I went to do my renewal I got another statement to cover the interim time, anda letter stating the balance that day.