15 hours ago, theoldgit said:

If your, or anyone else’s, wife lives in Thailand then that’s where they need to apply for their visa to visit Spain, she can of course fly there from the UK but she can’t get a visa from the UK.

A Thai national married to an EU or EEA national (such as Britons, for now..) traveling to an other countrt that is part of the EU/EEA can apply from anywhere on earth at the appropriate embassy. So a Thai-british married couple could apply for a Schengen visa from the UK.

 

Though some Schengen embassies seem to ignore this, just like the Spanish seem to ignore the simplified rules that apply to such a couple (no need for travel insurance, hotel or accommodation booking, police reports etc). 

 

There is of course the EU ombudsman Solvit. And writing to the EU about these continues violations via JUST-CITIZENSHIP {at} ec.europa.eu

 

 

2 hours ago, Donutz said:

A Thai national married to an EU or EEA national (such as Britons, for now..) traveling to an other countrt that is part of the EU/EEA can apply from anywhere on earth at the appropriate embassy. So a Thai-british married couple could apply for a Schengen visa from the UK.

Donutz is of course correct when he advises that a spouse of a Brit can, in theory, apply for a Spanish Visa when visiting the UK, but the Spanish are notoriously difficult and if a spouse is going to encounter difficulties she would, in my view, be better encountering those difficulties on home soil when time is on their side, not when visiting the UK when they are hoping to catch a flight.
Solvit is of course an option, I've succesfully used their service, but it does take time and not something I'd want to do whilst visiting a third country.
Of course nobody knows what's going to happen when the UK leaves the EU.

Indeed, it's best to apply from the country of origine (Thailand) but if that is not really an option one should know that under EU law you have (in cases like this,  they do not apply to regular thai travellers) the right to apply from the UK or elsewhere. And indeed Spain remains the most notorious for ignoring these EU regulations...