Have a print out. Skip any problems. Every city has internet cafes and any hotel reception your at will print for you. I have been asked. I had it. No issues.
As of yesterday entering on a SETV i will be here 1 year on exemptions and setv. Never even a question. I am not working and always have proof of funds.
There are too many efficient airports to count. Bangkok's airports have been rated some of the lowest in customer satisfaction surveys in recent years. Google it. As Thailands government has recently stated, they are trying to attract wealthier tourists instead of trying to increase the current numbers of annual visitors. Making people wait hours at customs is not a great start in sending this message out to the world. I think the OP has every right to be irritated at having to wait hours. It's a rational response. I am not sure he needs to be told to relax though. He seemed perfectly calm to me. I for one am grateful to people sharing their experiences here. We all should be.