What are the experiences and guidelines for applying for a type-O visa extension at the Singburi Immigration Office?

If you are applying for a yearly extension of stay based on marriage a thai you have two ways to meet the financials

bank 400K baht in an account in your name only for 2 months prior to your application OR provide a letter from your consulate stating you get 40K baht in income per month.

You need both the Kor Ror 2 & 3 marriage certificates, pictures of you and your wife standing in front of your address numbers, a couple pictures of you and your wife sitting inside the house and a few of the wedding too. You need a hand drawn map to your house, and copies of the relevant pages in your passport.

Once you apply and pay the 1900baht your application will go under consideration for 30 days and you'll get a stamp in your passport telling you when to return to get the year extension stamped in. At that time you can buy a re-entry permit too.

Unfortunately your wife is wrong, :/

You must use the immigration office in the zone where you live & do your 90 day reports.

A fair few years ago when they went to "zone immigrations" they stopped people from applying for extensions at any office they wanted to and instead made them apply at the office that services the area where you live.

This means unless you live in an area served by Singburi immigrations you use the bangkok office for your extension.

What extention are you applying for? Generally it has to be done at your local immigration office, ie where you live/staying