What are the application requirements and options for a Non-O Visa for returning to Thailand for 6 months?

A non-o will only get you 90 days then a 60 day visit Thai family.

5 months.

IMO not necessary as you will need 1 border bounce to get 6 months anyway.

I would:

Enter visa exempt 60 days.

Do a border bounce, some time after 30 days to get to 6 months ,(no extension on this 1st entry)

Then:

Entry gets 60 days.

Then extend 30 days locally.

Then extend 60 days visit Thai family.

7 months no issue.

And you won't have to apply for anything.

I married my Thai wife in the usa. if you did that you need to validate your marriage with state and local government, as well as the thai embassy before you can get a marriage visa.

There's not really a simple way to get 6 months without depositing 400,000 baht in a Thai bank account.

The non-O visa will only give you 90 days in Thailand, and from that you would apply for the 1-year extension. That extension will require you to show proof of funds in your Thai bank account (400,000 baht for marriage or 800,000 baht for retirement).

You do have the option of doing a 60 day extension for visiting Thai family based on your wife, but that would still only get you to 5 months.

You could possibly go on a non-O and then do a border bounce for a 60-day visa exempt stamp after 90 days, then apply for the 30-day extension on that. That's about 6 months but will require a border bounce out of Thailand.

The non-OA would give you a full year, but you'd also have to pay for a year of insurance and meet all the other requirements like a medical check, a criminal background check, etc.