Her sister got the visa spent the last 2 weeks here in the UK with us before all returning to Thailand.
December 2011, I applied for a settlement visa for my wife, the wait being a lot longer this time, but early March the visa was issued.
Just supply lots of info, pictures, Skype, msn, emails. Be honest and take your time.
To be honest, you will get all the help you need on here, I see know need to go though an agent. On each occasion applying my wife and her sister attended the initial appointment to hand in the hard copy and payment. And know further interview held.
Good luck.

Ken.p