I thinks the country trade most in bitcoins is no other than japan,because they are legalize bitcoin in there country and trading investment as part of there economics growth.Japan is most industrious country in southeast asia and digital currency is part of there progressive economy,thats why they called a growing tiger of bitcoin in the land of the rising sun,and we also know that the father of bitcoin satoshi nakamoto is living in japan,so in order that my conclusion is the best traders of bitcoin is japanese and no other than credit there  tittle as a bitcoin traders all over the world.