@Mike *****
I haven't mentioned using an agency in USA. Thanks for your comments though to consider all options. I have considered using an agency in Thailand but planning to apply here in the USA this time instead. I've been to Thailand 13 times already over the past decade but this is the first time considering the retirement visa option. I was asking about two topics:
1) Pros & Cons of Non-immigrant O versus OA versus METV
2) Experiences with the DC versus the Chicago consulate / embassy as I have the ability to show residency in either jurisdiction. Their websites show different requirements for the OA option.
Anyway, I've chosen to try the OA approach. Let's see how it goes.