IN Thailand

ATMs are great. They are everywhere. Most dispense 20 bills at a time. Bangkok Bank dispenses 25, making the maximum withdrawl 20-25,000 at a time. They give an OK rate as set by your bank, minus fees. My TD Select Account chages me ZERO ATM fees worldwide (except credit unions in BC oddly enough).

Don't change all your money at the airport. The difference is to little to matter. Money changers are everywhere.

The best rate is changing Travelers Checks, but for each check there is a fee (of about a dollar). That is why I suggest $100 or $500 notes. I only buy 500s. Travellers checks need a passport to cash them, (good to think about if you're sending your passport to an embassy for a visa)

2nd best rate is for cash.
Canadian cash gets the same rate no matter what size of bill it is. 34.88 was todays rate.
US cash gives 3 sets of rates lower for $1-5-10 bills, 20s & 50s get a bit better rate, and $100s get the fair rate.
Super Rich gets the best Cash only rate. Google it for the one location in Bangkok.

If the money is worn, tattered, or ripped in anyway, they won't accept it. Also if it's a older edition bill, it won't be accepted.