@Jarqco ***********
Good Luck to you in your return to Thailand as retired.
AND as your added question about the difference between the OA visa and O Visa requirements...ask your Thai Embassy in Finland.
There are differences and we will NOT try to explain them.
Easily to do for yourself by comparing the Visa requirements for Each Visa on the Finland Thai Embassy website.
You can read more about the OA visa and Non O Visa for retirement...
I have posted on your post
Topics of the
...OA visa home country
...And the Non O Visa.
CLICK on them and all posts regarding the topics will pop up to read.