Getting a ride from Chiang Rai to the border is very easy. There are many local buses that depart from the bus terminal in the centre of town. The bus ride takes about 2hrs. At the border town Chiang Khong tuk tuks are waiting to take people to the border crossing for a fixed price of about 60 baht.
At the border it takes no time at all to get stamped out of Thailand so long as you have the proper documents and didn’t overstay your visa. For about 30 baht per person you take a small motorised boat across the Mekong river to Laos. The ride only takes about 10 minutes. If you go to the Lao immigration on a weekend or after 4pm you’ll be charged an additional fee of US$1. At this border you can get a visa on arrival after filling out the immigration forms and paying the visa fee (US$30 for most nationalities).
The Laos border town doesn’t have much to offer other than the very highly rated Flight of the Gibbon eco-zipline experience. The weather wasn’t good when we were there so we skipped on it. Most people take the slow boat down the Mekong to Luang Prabang, we took the overnight bus. It left from the bus park at about 5pm and took about 15hrs to get to Luang Prabang. The roads in Laos are in pretty bad shape and wind up and over mountain passes. It’s almost impossible to drive faster than 50kph due to all the twists and hairpin turns, but somehow they manage to go very fast. I almost fell out of my seat a few times!
Scam Alert! There’s a common scam at the the border where people say the boat isn’t running and you end up spending night after night at the border. Don’t be fooled!