The currency in Laos is the Lao kip (code LAK). It is very hard to exchange it outside of Laos, and if by miracle you find a place willing to do so, the exchange rate will likely be very bad. Another option would be to find people headed to Laos, and exchange directly with them, but again, it would not be easy.
So make sure you change your kip before leaving Laos!
Mui Ne is known as one of the most beautiful beach city in Vietnam. It takes 250km in 4 hrs transfer from Nha Trang. There are many interesting sight-seeing that you never want to missed: Long Beach, Salt Field, Bau Truc Pottery, Pink Sand Dunes, White Sand Dunes.