How does immigration verify marriage for visa extensions in Thailand?

I assume visits are dependent on your office as I got a personal visit from immigration 1 month after I got my initial non imm O based on being over 50, not a marriage one.

what about agencies fixing a 'retirement extension' for baht ?

There must be something wrong with you if you've never seen your neighbours and they"ve never seen you

In my case they visited my house, while at the same time checking my neighbour's burmese maid. Simple 5 minutes, no problem, since then i have switched to retirement based on monthly pension as it is much easier.

In my case they requested a witness to be present (work colleague of my wife), not a neighbor. In any case the retirement option is less hassle, I guess.

I have Extension of Stay based on marriage for many years. Never had Immigration on visit, they sent local police. They filled out a report, had a chat, some pictures and off they went. They never talked to neighbors.

Believe me the neighbors have seen you. However, if O Visa for over age 50 (Retirement) works for you - keep doing it.

In my case, we lived in a rented house before, but were planning to move to my wife's house in her family's village after the marriage. The immigration did not care about the rented house, even though we lived there by the time of application for the extension, they wanted to come visit in the village where we would live after, I had only been there on visits before.

We served them lunch there and they wanted to see the village headman. He had to sign some papers. They took some photos of us in front of the house. Took about one hour in all, with no problems. They were nice and friendly the whole time.