I just visited the UK with my wife (Also Thai resident in Belgium), using her EU residence card as a visa equivalent. No problems, they are now applying 2004/38 properly. Just in case I took a wedding certificate with me to prove she is my wife, and my EU residence permit to prove I am able to use EU law despite being English. (As a non UK citizen, EU law applies when you go to the UK, but it only applies to Brits if they have used their EU rights of free movement in another EU state).
They sent me to an office where our paperwork was checked and the stamp given in her passport, but they did apply the law correctly and let us through with only a small delay of 15 minutes or less.
An entry office said there was something wrong with our paperwork, I said 'I don't think so', she said 'no visa', I said 'her EU residence card is a visa equivalent', they consulted the BCPI expert as per their process chart, she checked the paperwork, and issued a stamp.
I will always cross the border that way now, as its an EU right of free movement, rather than a courtesy of the UK.
And of course the same applies in reverse, when Brits visit Europe their wives need a visa, but a UK issued residence permit (which can be a stamp in a passport) is a visa equivalent for short stays for family members of EU citizens.
---------- Post added at 10:04 ---------- Previous post was at 09:53 ----------
Just to confirm that from the French embassy site.
CHANGES TO THE LEGISLATION: FAO family members of EU nationals:
Married spouses and children under the age of 21 or dependant of EU nationals are exempted from obtaining a Schengen visa to travel to France if they hold:
a valid travel document, i.e. passport;
a valid UK residence permit with the endorsement "family member of EEA national";
and if they are joining or travelling with the EU national.
However if they do not satisfy the above conditions, they need to apply for a visa to travel to France (for instance if their UK residency does not state those exact words/ the EU national is not travelling).
This exemption only apply to married spouses/ children under the age of 21 or dependant, i.e. not to parents - for further information and procedure to apply for a visa as the family member of an EU citizen, click here (…) nor to unmarried partners, civil partners - for further information and procedure to apply for a short stay Schengen visa, click here (…)
Family members of French Nationals are not included in this legislation and still require visas to travel to France. Click here to apply for a visa as the family member of a French citizen, click here (…)