Well the most adventurist and scenic way to get to LPB Laos, would be a slow boat or fast boat down the Mekong. You need to get up tp Chiang Rai area of Thailand.
You dont mention where you have been in Thailand and what your interest are? Trekking? Indigenous Villages? National Parks?
You could also explore Chiang Mai, the old capital of Thailand, on the way to Chiang Rai.
Do you have a guidebook on SE Asia?
From LPB Laos, you would head south to Vang Vieng, a popular stopping point and party town, as well as outdoor adventures, then head to the capital Vientiane, from there, get to Pakse, here you can rent a motorbike and a do a huge loop in the Bolevan area, via Salavan, Sekong, Attapeu, which has small villages, lots of waterfalls and mainly rural roads. 3-4 days is nice ride loop.
Then from Pakse, shuttle to 4000 Islands areas and waterfalls. Now you are close to the Cambodia border.
