For the op's info, CM immigration has been pretty empty so may be quick to get your answers from them. Also, there are two assistants just before going in that checks all the paper work and may be able to assist you.

Appears he is in Chiang Mai (Doi Saket). Friend just did his in Chiang Mai, his first extension based on retirement, with no problem. He just followed the list from them. Took him only an hour as it is not very busy here now.

There are 3 new short forms to fill out but they are for everyone doing extensions. 1 for requesting permission of stay, 2nd is list of penalties and 3rd don't remember. About 5 minutes to do them.

No, stopped working and he is aware. Contract not renewed due to government funding loss.

I'm going to the airport one tomorrow after someone in another group said that was the place. Will post back the results. Work permit now renewed.

A colleague at work converted his permission of stay based on work to one based on retirement at the airport one recently.

Yes. Been renewing extension and WP for more than 2 decades so nothing has changed regarding this.

Thanks re the extension. The brochures don't make it that clear, at least to me. 😊

If Chiang Mai, I just did my mail in and new receipt returned to me just 3 days ago. Since Chiang Mai has an office at airport road and at Promenada, I used the same Airport address successfully.

The Chiang Mai info may be useful for others in case you are referring to Bangkok mail in.