Alen, I think you should first ask advice from the person who issued the invitation letter. Ask if they can advise you of the procedure you should follow to accept the invitation. And then also ask the nearest Thai embassy. Good luck
thanks James. My pensions more than cover the monthly income requirement, and they will be transferred to my Thai bank account for me to live off. It's the other requirement, everyone is now saying is necessary, that I can't do.