Here's how you can get a foot in the right direction:
1. Check the price variances at coinmarketcap:
https://coinmarketcap.com/currencies/bitcoin/#markets. The fiat denomination should tell you where the exchange is. CNY you can ignore since they'll all be out of that list soon.
2. You can do this for a period of a month at least, but as of relatively recent weeks since July, the markets have been highest at South Korean and Japanese exchanges.
3. Judge the volume for yourself. If you can a) have enough volume of fiat and coins b) be registered with the exchanges, you're on your way.