The official national currency in Laos is the Lao kip (LAK). Although only kip is legally negotiable in everyday transactions, in reality three currencies are used for commerce: kip, Thai baht (B) and US dollars (US$). In larger cities and towns, baht and US dollars are readily acceptable at most businesses, including hotels, restaurants and shops.
In smaller towns and villages, kip is usually preferred. The rule of thumb is that for everyday small purchases, prices are quoted in kip. More expensive goods and services (eg long-distance boat hire) may be quoted in baht or dollars, while anything costing US$100 or more (eg tours, long-term car hire) is quoted in US dollars.
Despite experiencing relative stability in recent years, the kip cannot yet call itself a stable currency. As such, prices in this guidebook are given in the US dollar equivalent.
The Lao kip is not convertible to any currency outside of the Lao PDR. Because of this, the only reliable sources of foreign exchange information are those inside the country.
Read more: http://www.lonelyplanet.com/laos/practical-information/money-costs#ixzz2sirzK19y