Laos is offering Visa on arrival at the border crossing and at the airport. If you travel by bus from bangkok, you may not allowed to use the Nongkhai-Vientiane bus without a s Visa (they just dont want t o wait for you). So take a tuktuk to the border, get the visa and get a taxi or tuktuk to the city then.

12 months multiple entry visas are only offered to people with a Lao work permit, their spouses, to investors and diplomats. It is not that easy to get as it is in Cambodia.