How long should I request for the extension on my Non-O Visa when applying for a Married Visa in Thailand?

David - is it a 90 day Non O? I could not apply for a marriage visa when I was still in UK - so despite being married to a Thai I had to apply for a 90 day Non O Retirement and when I came to extend to 1 year they would only let me extend on a Non O Retirement - citing that your first extension has to be of your original extension.m - you can only change after the first year which is my intention. I will no doubt be corrected but that was what the Immigration Officer told my wife in June. I would be keen to know how you get on.

and for the reason for the extension don't write a novel 😮 I saw one guy wrote like a paragraph of reasons etc, Just write

Thai Wife or Marriage to a Thai

If your Non-O visa states the reason it was issued then your first extension must be for the same reason. You put 365 days

I assume your Non-O is a marriage visa because if it was not issued for marriage you cannot get the first 12 month Extension of Stay based on a different reason to the initial Non-O.

It’s a yearly extension so 365 days

You are going to apply for a 1-year extension based on marriage to a Thai. So put 365 (days). or less.