I wouldn't worry too much, next time make sure you can show all the requirements they might ask for, hotel reservation, 10k bath in cash (if i remember right, maybe 20k), and a flight out.
also if you can show a bank statement in paper with money on the balance they will backoff very quickly.
just make sure to stay polite and friendly and simply explain your situation making sure they understand you are not coming to work, this is their main concern in the end.
oh and dress a bit like pants and shoes so that you don't look like a hobbo, they will react to this.
maybe throw in a girlfriend in there ... ????
also maybe get a flight to another airport, the immigration ladies at Suvarnabhumi are the worst from my experience...
this is the kind of cases where you have to understand the "not losing face" thing ... they need a way to change their mind without losing faces.