It depends on your luck, sometimes you will meet a angry one and he or she can refuse to let you in. some might ask you to show a return ticket or hotel booking or if you got
*****
b cash. some will ask, if you are working in thailand etc etc....
You can fly in, just ask your girlfriend to be prepared to answer the phone 🙂 The immigration will stop you and ask you why you are flying in and out. Tell them your gf is thai. They will ask you to call her... will work for a while. after a few more times. they will ask you : get marry.... (that is why i got married.... ) ((take more pics of u 2 together, might help if you get pull over.))
bring husband to immigration, you will get 60 days extension for 1900b. than go apply for non o (try to bring all documents and 6 pics of you in your house.)