You should never exchange more money than absolutely necessary at the airport, because you always get a terrible rate.
In Departure, money exchange booths know they have you cornered. You don’t want to go home with foreign currency, and will take lower rates just to get rid of the local currency.
In Arrival, currency exchange booths play on your fears that you won’t be able to get a good rate at a “safe” place later; and also play on the fears of travelers who don’t want to use ATM machines.
For example, the airport exchange was showing 32.86 baht/USD.
I used my capitalone venture rewards card to purchase a pizza before getting to the airport. I received a rate of 34.93.
While I was at the airport, I needed cash from the ATM. I withdrew 20,000 (plus the 180 fee), and was charged on my Schwab no fee atm card, the reate of 34.81. Not as good as my capital one credit card, but still better than the rate I would have received at the airport.
Stay away from airport currency exchange booths. If you absolutely must exchange money here, exchange only the LEAST amount you can get by with …