I live and work in Thailand with a visa based on marriage. I usually submit my renewal application in late November (the process takes months). I am going to the UK soon and was wondering if I was able to renew my visa (based on marriage) at the Thai Embassy in London. I had heard that the Embassy requires a lot less paperwork than I usually need to provide at my local immigration office. Any feedback would be appreciated.

Apparently you are applying for a extension of stay (it is not a visa) based upon marriage at immigration. You cannot apply for a new one at any Thai embassy or official consulate.

You can only apply for a new non-o visa at the embassy that will allow one 90 day permit to stay.

20 hours ago, danny42 said:

I live and work in Thailand with a visa based on marriage. I usually submit my renewal application in late November (the process takes months). I am going to the UK soon and was wondering if I was able to renew my visa (based on marriage) at the Thai Embassy in London.

As joe has said you have an extension of stay (a visa can never be renewed) and that can only ever be done in Thailand 

 

The standard is that you can apply up to 30 days before, depending on the immigration office the under consideration period may well be (in udon it usually is) till 30 days after your current extension finishes.

 

That is anything between 1 month and 2 months (hardly months, I feel) 

You can get a re entry permit for the under consideration period, so depending on the actual expiration date of your permission to stay you should be perfectly able to visit the U.K. and return before the under consideration period finishes.

 

I am likely to need to do exactly that as my extension expires on May 15th and I have a wedding to attend on June 6th next year. As that is guaranteed to fall within the under consideration period I will either have to guarantee a return before June 15th or see if the IO will extend the under consideration period next year.