@David **********
okay, the fact you've never been asked for proof of funds, onward travel or a hotel booking when stamping in (while anecdotally interesting) doesn't mean that nobody is asked. So let's just get that straightened out right now.
Also there are two times you usually show proof of funds,
One is when you are at a thai consulate BUYING a visa to thailand, if you are required to show proof of funds there you show a bank statement.
Another one is when you are stamping IN to thailand, if you are asked for proof of funds then you show 20K baht or the equivalent in CASH, you cannot show a bank statement or credit card.