Baht

That's not even $200 US!  

Being that we take regular trips to Thailand, we usually try to always keep some Thai Baht on us.  4000 - 6000 baht is good.  That way, when we arrive in Bangkok, we can get going without exchanging money or using an ATM at the airport - not that there's anything really wrong with that.  We just like to get into the city as quickly as possible.  And there are plenty of banks and ATMs to conduct business after we're rested.