I think Malaysia have stable currency compared to the other two.
Fiats are fiats, if you check real actual value and fiat index, you will know fiats are not just unstable, even the so called Malaysia fiat is not stable at all.
The other two countries could use bitcoin as their main currency but the problem lies with the implementation.
It is not possible for a country to use bitcoin as their currency, they will still prefer their fiat. But that does not stop bitcoin from progressing because bitcoin is not a country coin but world coin because it is meant to be decentralized. If people from a particular country like, they can hold bitcoin which is better than fiat.
In most cases that couldn't be done.
For now it is in all cases, and no case ever like that in a way country will use bitcoin as fiat.