where exactly do I wait on arrival at the airport for my my wife to pick me up in her car?

At arrivals

Arrival level, outside the terminal building next to the road. I believe it is still the second road at the back where private cars are allowed.

You do have options though. There is 10 doors to exit so better to tell your wife which door you are waiting.

There is no parking at arrivals so your wife needs to wait further away in the roadside for you to call or drive loops which is not that convenient. I personally just park in the short term parking, short walk to terminal and wait at the arrival meeting point at door 3. Meet and greet my friends and take them upstairs and to my car and off we go.

The security chaps do seem quite enthusiastic about moving vehicles along, as noted above I would simply park in the short stay. IIRC it's 20Baht an hour

Do what I do.

Call the wife when you get out of the plane. Agree on a time. Tell her to meet you on the Departure level at the beginning.

Entry 1.

You should be there just before her. You spot her and wave her down. Chuck your gear in the back, kiss her well and off you go home for great so-good-to-see-you-again-sex

Forget about Arrivals. Dark and murky place with a lot of annoying people.