Applying for OA visa. Does anyone know what the process is for adding a new spouse to the OA visa?

My bride to be is a 40 yr old non-Thai — who would not qualify for a retirement visa on her own. 

TIA

The procedure is:

1. After you receive the Non OA visa, you apply for a Non O visa for your spouse at an embassy outside Thailand. (A Non O visa can often be applied for at Immigration inside Thailand, but not in this case.)
2. When the 90-day permission to stay on the Non O is near an end, your spouse can request an extension of stay (piggy backing off your permission to stay based on the OA visa) which ends on the same date as your permission to stay (initial or extended).

It is reasonably straightforward, as I understand it, as long as the Non O visa is applied for outside Thailand.

6 hours ago, BritTim said:

.....as long as the Non O visa is applied for outside Thailand.

Indeed.

I've always been slightly confused on the "piggy back" for eg non Thai spouse.

Few folk ask about it after arriving on TV or visa exempt. 

She would need to obtain the non O prior to entering thailand..