@Paul ************
being Married has no bearing on the Visa ...as it states for the UK ...she can be just your girlfriend...spouse or civil partner .
You should always start with a 6 month visitor visa ..maybe do that twice ...most importantly is you show she has a reason to go back to Thailand...ie good job...house ...children ...get a letter from her employer stating how.long she worked there .
Don't transfer any more money...you need to show you UK balance ...she doesn't need any money as you are her sponsor .
Paul King is someone that I trust .
But I've done 3 visitors visa....2 visa for 2.5 years and the life in the UK for my wife so she now has ILR and next is a British passport ....it all takes time ...and you need to give MORE INFO THAN THEY ASK FOR ...
BUT...the most important thing is ...your bank balance and a strong reason why she will return to Thailand