@Jenny ******
There are usually two times you are asked for proof of funds and they have totally different requirements
One time you'll be asked for proof of funds is at the thai consulates that require it to buy a visa, in that instance you must show a bank account and CANNOT show cash
Another time you'll be asked for proof of funds is by the officers at passport control when stamping into the country, in that instance you must show cash and CANNOT show a bank account.