Vientienne accepts baht, U.S. dollar and the local currency is Lao Kip. I would bring baht to pay for your hotel but use Lao kip for restaurants and other stuff. When I was there, it was at 10,000 kip for $1. Most of your kip come in denominations of 5,000 kip (50 cents)Very hard to spend more than $20 a day here and note that 500,000 kip will give you enough bills to stuff all of your pockets. Give some of your lower denomination bills to the local kids. The kids are polite and will thank you with a wai (unlike the savage kids in Cambodia) . Remember that no other country accepts kip, so exchange nay leftover money before you go or it will be a new souvenier. Money exchange places are all over the city and the rates are comparable to the banks.