Gifts are not taxable to the receiver. And you do not need to report any gifts that you give unless the amount is more than $14,000 per year. So if you want to consider this as he gives you $2000, and you give him some merchandise, there are no tax consequences.
However, what you are describing is not really a gift transaction. You are describing being in business where you are facilitating international money transfers so that your friend in Vietnam can buy US goods with a US bank account.
If this only happens once, then you probably don't need to report it at all. You just need to be careful that this is not a scam.
If this is going to happen a lot, the safest way to do this is to open a separate bank account for this business, do not use your personal bank account. If the amount of money you receive is more than the amount of money used to buy goods, then the difference that you get to keep his taxable income for performing a service and you would report it on schedule C.
if the bank account is purely a pass-through account and the outgo is exactly equal to the income, then you won't have taxable income, but you may still want to report it as a business on schedule C. With the income equaling the expenses, you will show zero net taxable income and owe no tax, but you would be reporting the activity as a business activity which may avoid any misunderstandings with the IRS.
