Denied entry to Thailand!

Guys I really need some advice here as I feel like I am being treated very unfairly. Basically I left Thailand and went to Hanoi, Vietnam for 5 days. While I was there I applied for a new Thai tourist visa. I supplied the embassy with bank statements ect. I was given my visa the next day, and headed back to bangkok. Immigration stopped me and said what are you doing here. I said traveling. The lady replied with I dont think so, you have been in and out of the country for a year now. They put me in a detentions cell over night which I had to pay for and made me pay for a flight back to Hanoi. Their reason for doing this was that I didnt have 20K baht with me in cash? I arrived back to Hanoi and was told that I can either pay 140 dollars to stay for 15 days or pay for a flight back to the UK. The immigration in Thailand said I can come back in two weeks time. All of my belongings are there. Ive wasted so much money due to them messing me around saying that I never had enough money, when most of it was in my bank account which I had told them. Anyone have some advice please?I know they are obviously just making my life difficult for me because I have had a few visas but there is no law stating how many visas you are allowed. I broke no rules, was granted a visa after showing the Thai Embassy my earnings. Yet I get told I cant come in because I dont have enough money? After being told to get out of their country and go back to my own. Tourists are Thailands main income, and now to be honest its put me off wanting to go back.