Sometimes when travelling through more than a couple of countries you can end up with currency from a country you visited earlier that has a lousy exchange rate in your current country due to a wide spread but might have a good rate / narrow spread in a country you intend to visit.
I'm wondering if there are some tips for finding out typical exchange rate spreads for various currencies in various countries?
This is my question, below follows my current example, but please don't submit answers that just address the example since I want to know general methods. And of course I realize rates vary in many ways from place to place, bank to bank, etc.
For example I'm left with about $250 worth of Malaysian ringgit in Thailand that I didn't change at the border because I thought I'd be in Bangkok later. It turns out that to change this money to baht in the non-tourist places I've been in will cost about $20 even though spreads for currencies like US dollars are very good.
So I'm wondering if there's a way to see what kind of spread to expect in Laos or China or Burma or Cambodia where I'll be in the coming months and could change my ringgit for the local currency.