Yes as of the moment bitcoin and other cryptocurrencies were not yet illegal in Vietnam but based on the news I ran into this will no longer be the case by next year. You have to listen to your parents because Vietnam will not just ban this kind of currency but will also impose penalties that are really high to those will be caught patronizing such. I believe it was your central bank that announced it. Kinda odd for me because a friend told me that certain university in Hanoi allowed bitcoin for their tuition fee payment. You should watch out for more news in your country for the progress in this issue because it's a country per country discretion. Goodluck!