Hi there
There are quite a few posts on EEA Family Permits on this forum so far, for example here:
http://immigrationboards.com/viewtopic.php?t=114867
I'm not sure about the specific process and documents that they require in Thailand, but for the general guidance from the UKBA you can see this link:
http://www.ukba.homeoffice.gov.uk/eucit ... /applying/
I would recommend that you/your partner emails/calls the British Embassy in Bangkok to see what info they specifically require. The Embassy in Beijing need many more documents than they should. But some of the people I know just provided them all (Sorry, I don't have a list).
As long as you are working in the UK you should be fine, but make sure to keep all your pay-slips/contracts etc. You will definitely need these later. They will also definitely ask for proof of your relationship (marriage certificates) and proof of your nationality/citizenship (copy of your passport). The British Embassy in China also asks for proof of funds and, if I'm not mistaken, proof of your accommodation (I may be wrong), but I'm sure they ask for more than the EU Directive actually requires. Some people say that we shouldn't provide more than the requirements, however, if you don't you're likely to get locked in a length appeals process and things will get delayed. It's up to you how you deal with this, but I'd just give them what they want, if I had it.
I guess applications in Bangkok will go through VFS,
http://www.vfs-uk-th.com (as they do in China) but again you could email the Embassy and confirm.
I have heard of some people being interviewed for the EEA Family Permit (I think one guy wrote about his Indonesian wife being interviewed a few weeks ago). The Embassy can do this if they wish, but I'm sure that they don't do it all the time.
Again, best to hunt down the Embassy staff in Bangkok directly...ask specifically what they require.
Perhaps someone else in the same situation as you can give some more help?
Wishing you all the best
Chaoclive