It’s very difficult for me to advise European readers what to do given that you can’t buy Vietnamese currency in many places in Europe. I have to watch that I don’t say something that’s incorrect or impractical.
So you need to take responsibility for acting on what I say here and know as well that I am not an accredited financial adviser or even a person who has paid a great deal of attention to financial matters. So caveat emptor please (let the buyer beware).
You can buy dinar and dong from Treasury Vault (http://treasuryvault.com/). I personally prefer Vietnamese dong.
If you place an order with TV, you’ll need to go to your bank to make a wire transfer. Here in Canada that costs $30.
You’ll also have to pay the Fedex delivery charges. Here in Canada that’s $49.
There are other places to buy dong such as a popular Internet retail buying and selling site (I don’t want to be responsible for naming it). I have no idea how reputable or dependable they are, but several people have told me that they have purchased dong there and all has been well.
If you can’t purchase dong in Europe, then I wonder if you’ll be able to cash it in? You may need to buy dinar even though the return is lower.
Again proceed on your own recognizance. Do your due diligence and be responsible for what you do, please.