I have never had to prove I am carrying any kind of money in 24 times of travelling to Thailand. Obviously, you would be pretty stupid not to come without some cash. I always bring enough cash for my holiday. I'm just more careful how I look after it. Thailand is very safe but no matter where you are in the world, there is always that one time.
Why do people keep trying to circumvent the system then cry to a Thailand visa group asking for help. Do things properly in the first place and you won't get any hassle.