Can I register my first 90 days on a multi-entry O visa in Thailand?

In fact looking at the image of the passport page of your entry stamps ALL of them are for 90 days only. NONE are longer,

Here is an image of your visa with the personal data redacted;

As you can see it's a year-long, multi-entry Non-O visa issued in Yangon, it has NO notation in the remarks but was issued for marriage to a thai (seeing as Yangon doesn't sell that visa for retirement) 😕

The VISA a multi-entry and is good for a year <- meaning you can come in and out all you want during the validity BUT on that visa you can ONLY get stamped in for 90 days, period end of story.

Then when that 90 days is running down you have three (possibly 4) choices

-You exit/re-enter the country to get a new 90 day stamp

-You apply for a 60 day visit thai family extension for 1900baht at the immigration office

OR

-You meet the financial requirements 400K baht in a thai bank account in your name only for 2 months before you apply for a marriage extension and you get a year extension for 1900baht at the immigration office.

You might be able to get a 60 day covid extension but that is immigration office specific all you can do is ask. BUT you either get an extension or you leave and come back.