Hopefully I won't get flamed for asking a dim question but can't find the answer

Myself and my wife (British) intend moving out in March, we have spent a lot of time there so know the basics

Plan is to get 3 month non O before we arrive

We have the money to put the 800k each in the bank but the agent route means we can leave our money at home earning something and also an easier life

If we used and agent would we pay the new retirement visa price or the extension price as we already have a 90 day non O ? Thanks

Heads up.

I have just been to the new Chiang Mai immigration office for letter of residency. Informed that it is now taking 4 weeks.