You need to supply your original passport if I remember from last year.
We have three council tax letters addressed to both of us and I was going to add 6 other letters addressed to only my wife and 6 address only to myself- will this suffice?
It should be as 6 of each individually are what is required or 6 in total to the two of you.
My payslips and P60 are colour printouts printed at home as thats the only option I have, it was ok for the first spouse visa will it be ok again?
If they were fine for the spouse visa they should be fine for FLR. I haven't seen a P60 from the taxman for years and can't remember what one looks like. I would be happier with an original, if it was me. Can you get a copy from the taxman?
Should we add her Thai ID card, translation and copy too?
We supplied a copy. No translation needed. It has English on it too.
NHS surcharge needs to be paid first as you need the IHS number for the visa application.