Recommendation: Bring lots of reading material .
The journey from Thailand to Laos via ground transportation is beautiful, but very long! I left Chiang Rai, Thailand at 6am. First step, I paid $2 to take a 3-hour bus ride to Chiang Kong where I went through immigration to leave Thailand and formally enter Laos.
Once across the border, I took a Tuk-Tuk shuttle to Huay Xai. Once I arrived in Huay Xai, I got in one of the slow boats and sat tight for the next 7 hours until we arrived in Pakbeng where we spend the night.
The next morning, we reboarded the boat for another 7 hours. When we finally arrived in my Luang Prabang, I hadn't pre-booked accommodation, so I wandered around town until I found a hostel called “Friendly” for $4/night. It was a great spot!
The journey via boat ride was calm, scenic, and eye opening to pass many tiny villages. If you don't have a time crunch, it was a unique experience. My #1 tip is making sure you get a seat in the front or middle of the boat... the second day I got stuck in the back next to the very loud, open engine which got annoying very fast.