I am here from Australia, my bank provides fee free credit and debit cards. It pays the 220bht ATM fee. I have an App that gives me the daily exchange rate. I have Google wallet on my phone and Villa and Big C Supermarket chains allowed me to swipe. For all the hassle involved I don't bother carrying heaps of cash. Unless you are in the country side order drinking and smoking in shady bars. I wouldn't bother with heaps of cash. In Bangkok I use a travel card on the train and the Grab app for most taxi rides. The motor bike rides cost 20-25 bht. I just drawer 5K from the ATM as needed. Yesterday my bank exchange rate was 22.
***
on the 3000bht I withdrew. The ATM offer was 21.
***
, and the money changer offer was 21.9. The Australian bank official rate was 22.9. Do yourself a favour check your banks and get a card with no fees, large amounts of cash also leave you open to having it stolen.