I am British while my wife is Thai. We've been married for 7 years and have a son together (who holds both a U.K & Thai passport).

 

We want to apply for a Spanish residency visa for my wife and we are told: "Thai spouses of UK citizens will have to submit the UK marriage certificate (Court recognition) if they want to apply for EU spouse visa."

 

We are currently in the U.K. How do we proceed to get this?

 

I've searched high and low online without luck. Any advice is much appreciated.

this may help - https://www.whatdotheyknow.com/request/standard_letter_confirming_that

The simple answer to the title of the thread is you cannot.

It is the Thai certificate that is considered valid and you cannot be married twice.

Sadly the Spanish authorities have got a bee in their bonnets and about all you can do is present a copy of the document linked above.

The British authorities will not confirm the authenticity of a foreign marriage certificate nor will the courts.

 

I found this with a simple Google.

 

https://www.gov.uk/guidance/notarial-and-documentary-services-guide-for-spain