The authorities in his country will ask where his funds are from and if he can't produce anything or documents to prove it's from a legit business transaction, his funds will be seized.
If I were him I could just contact a close relative outside the country to send my coins to them. Everybody has a relative somewhere but I guess this is a matter of trust still. And then ask them to convert it to digital cash and send it back.
If he can buy some expensive things from a foreign country, such as computers or electrical tools, and he ships them to his country, and there he sells them and gets their price, and so his money will become completely legitimate. In addition, he can make an additional profit by selling this commodity at a higher price.
I think that this is the best solution, so no one will be able to ask him about the source of his money, because it will become completely legal.
And how many times do my relative has to send such gifts?
Even if I get some commodity, why would someone buy it at higher price from me?
And what about the tax on profit that I will earn by selling that commodity.
I think you haven't considered all the aspects before suggesting the solution.