Big adoption in Vietnam, Cambodia, Laos wouldn't surprise me.

They use a non-fiat currency already, the $US for most of their transactions. By non-fiat I mean it is not fiat to that country.

So they could move over to any currency, including BTC.

I also noticed travelling through these countries how well connected they are. Wifi is everywhere and it is free. So someone with a cheap smart phone can get free access fast enough to send/receive transactions from their phone.