What are the visa options and requirements for a couple planning to live in Thailand for a year, especially regarding the OA and O visas?

Your wife will also need to buy a re-entry permit single or multiple once she has her extension in Thailand if she wishes to leave the country at any time before the extension stamp expires to keep the extension alive. You will need the same when you are on your final entry before your visa expires in the second year if you milk the timing.

The way it works IF you both get the visas in your country (You the year-long, Non-OA and your wife the 90 day Non-O is

YOU would apply for the OA visa online at the thai consulate in your country before you wing your way here and your wife would apply for a 90 day non-O visa (based on being the spouse of someone on a long stay visa)

When you guys enter you'll get stamped in for a year (or as long as your mandatory health insurance is good for) and your wife will get stamped in for 90 days. When that 90 days runs down to 30 days or less you go to the immigration office where you live and apply for a yearly extension based on "trailing spouse" (a foreigner married to someone on a long stay visa/extension).

She will get an extension that matches how long you were stamped into the country on when you entered on your OA visa. There is no financial requirements for her to get that.

BUT

There is a requirement that you need to have the marriage certificate "legalized" in the UK before you come here if you want her to get a matching extension (it is NOT a service the UK Embassy here in thailand does so it has to be done before you come here OR you mail everything back to get it done)

You get the certificate legalized in Milton Keynes and then you get it stamped at the thai embassy in London.

as already stated the non oa will need insurance .

do you have a Thai account with the 800k in it?

makes everything much easier

The major benefit of the non-o vs over the non-oa is you don't need to have insurance cover (that meets Thai requirements) throughout your stay and for extensions. The non-o is much cheaper in the long run. Most long staying people over 50 find it easier to arrive on a 60 day tourist visa (NOT the Special Tourist Visa) then transfer that to a 90 day Non-o in country and meeting the requirements of depositing 800k into a Thai bank. You also don't have to leave every 90 days and you can draw that 800k down to 400k after you have a 12-month extension.

After your wife gets 50 years of age, you both can apply for the Non Immigrant O-A visa but both of you need to meet the requirements.

There are less requirements for your wife to apply for the Non Immigrant O visa based on being your dependent and get 90 days of stay on arrival which can be extended with another 9 months at a Thai Immigration Office after 45 days of arrival, this to match your stay you got on entry.