You need to show your gf has reason to return to Thailand, Job, dependents, assets. Your circumstances are not so relevant, just maybe a letter / statement saying she will stay with you.
Bringing a dependent to the UK now requires something near to a 30k a year in come and will tie again soon. UK government has an issue with us bringing our loved ones to the UK apparently. ...google is better than Facebook for facts
Lloyds bank for example has an off shore banking service maybe you can get an account there? Sure other banks do too, but yes best for driving licence etc too is to mention a UK address via friend or family