I'm coming to the end of my first Non Imm 'O' Married Visa on 14th November. As I understand it I have to submit my extension to cover the next year, a month prior to the cut-off date. In my case this would be14th October. It's also the school holidays and I'm trying to plan a few days away(still in Thailand). Do I actually need to submit my extension application on 14th October or do I have a window either side of that date?

If the non-imm "O" married version is the same as the unmarried version you can typically apply up to two months before, in Phuket anyway.

If the non-imm "O" married version is the same as the unmarried version you can typically apply up to two months before, in Phuket anyway.

One month ago they told me at the Chiang Mai immigration that you can do your application 30 days before the expire date. In your case you can do the application from 14 october, but you can also do your application on 12 november.

I did mine application one month ago. Do not forget to bring a photo with you and your wife on it. They want to have one.

You have to do it before the 15th of November. Immigration advices you to do it early, as early as 30 days before the end of your current permission to stay, as in case you are missing some documents you will have time to sort it out. Never wait till the last day. An extension starts from the date your current permission to stay ends, so you don't lose any days.

Doing it around the first of November would be fine.