What steps should I take after receiving a 90-day Non-O visa based on marriage in Thailand?

The Non-O marriage visa IS a 90 day visa. Before the end of the 90 days you need to return to immigration with all the same paperwork (updated) and apply for a 12 month extension of stay, you'll also need to show you have 400k baht in your account for 2 calendar months prior to the day you apply. Your application goes under consideration for a few weeks and then you return to get the remainder of the 12 months stamped in, they may want to visit you again during the under consideration period

It sounds like you have gone from a tourist entry to a non-o based on marriage, 90 day visa.

Which is the correct process.

The next step is 1yr extensions, about 90 percent the same documents you just used.

You will now prepare for the 1 year extension, which can be done at 45 days or when your money has been in the account for 60 days.

The handout is available in room 204 ( which you probably used) has all the requirements.

If you don't have it you can find it here

This is the normal process, sometimes a little confusing.

The initial Non-O Visa is 90 days