What is the process for switching from a Non-O foundation volunteer visa to a religious (RA) visa in Thailand?

There is no "followers" option, everyone cancels their current extension, everyone goes to a thai consulate outside thailand and everyone applies for a visa.

If you go to a thai consulate that is eVisa, sadly you might have to apply for your visa FIRST, get it approved and then apply for your wife's / child's visa after that <- as your visa is needed to show why they need theirs

Where as If you go to a walk up consulate (like Taipei) you can all apply at the same time (because it's in person application

You're not on ANY Non-O visa anymore, you're on a yearly extension of stay based on volunteering (just like your stamp says "extension of stay permitted until")

AND

while you can "change the reason" for an extension for a lot of things, you cannot go from a volunteer extension to a religious one..

You would have to cancel that extension at the immigration office that issued it with documentation from the foundation that supports it saying you will stop on xxx date

THEN

You would exit the country and do one of two things

1 - come right back in on a free 60 day entry stamp, get documentation from who ever is supporting the RA visa and apply for it inside the country at the immigration office where you are located

OR

2 - go to a thai consulate in a nearby country and apply for the visa. Almost all the consulates nearby are eVisa online system consulates now, <- meaning you go to that consulate, you apply online, upload your documentation, pay

THEN

you wait in that country for the visa to be approved and you to receive the email that has the PDF file which is your visa.

You'd print that and then come in to thailand presenting it with your passport when you enter and get stamped in on the RA visa

Another option is to go to one of the FEW thai consulates on this side of the world that are "walk in" apply in person consulates, like Taipei (which you just show up and apply) or Yangon (which requires an appt to get in the gate) and apply in person.

Those would be your choices,

Check with your immigration office IF you can even get a Non-Immigrant Type RA visa issued inside the country from a free stamp entry because if you can't you go out of the country and buy the visa from a consulate nearby