I had an OA for 6 years. I have Thai insurance. Even when I was married I chose to keep the OA as a retiree. The extension process is much easier. If you can afford to keep the 800,000฿ in the bank this is the easiest thing to do.
Technically I am resident of two condos. The contracts are overlapping. After December 22nd though you will be correct.
I usually give a heads up to the owners before I leave the country so they will be prepared to submit the request in time. I will see how this works for the new condo. What is acceptable depends on your immigration office. I use the Bangkok immigration office.
I got a TM30 from my old landlord in 2 days after returning from the US.
I got my TM30 from my new landlord after waiting 2 weeks. I’m hoping it’s just a first time thing because I just moved in. Fortunately I don’t travel outside Thailand all that much and don’t need a TM30 very often.
For a 1 year retirement extension the 800k must be in a Thai bank account for 2 months before you apply for the extension and 3 months after you get the extension. It cannot drop below 400k after that. You will need to bump it up to 800k again 2 months before the next extension. Different immigration offices may interpret the rules slightly differently so check with you immigration office.