Best place to find Thai G/F probally not in a Bar! If you meet family make sure you take plenty of coin as you will need it! as when you are in Esarn you will be expected to pay for eveything and i mean everything!
They will invite all there friends round for dinner and a party all paid for by your goodself and will expect a donation before you leave!
As for a tourist visa it will take a lot of time and effort on your part, my friend is trying to get one at the moment, you need to be sending regular payments to her and all documented of course, telephone records, bank statements to show you can support her whilst she is in your country, photo's of every room in your house! Also they might ask a letter from your parents to say that they know about the relationship between yourselves and that they approve!
All this becomes very tiring and costly after a year or so, so think on!