Thank you for your question!
After we obtain the visa approval letter for you, we will forward you a copy by email. The document will also be sent into and recorded at the data base of Vietnam Immigration checkpoints at International Airports. Your visa thus will be easily stamped onto your passport upon your arrival.
You can make payment by any currencies but in USD is the most preferred.
For applying Vietnam visa on arrival online, you can choose single or multiple entry according to your trip plan. Both of these kinds of visa work well.