The Mekong river marks the border in between Thailand and Laos , so in order to go from Thailand to Laos by road, you either have to take a boat when you reach the Mekong river or you can take one of the bridges that link the two countries.
There are two bridges in between Thailand and Laos, called Thai-Lao Friendship bridges.
The first one opened in 1994 and is in Nong Khai, from there you’ll reach the capital city of Laos, Vientiane. I never went there so far, and therefore I’m unfortunately unable to post a picture of it. But I’m sure you’ll find plenty available on the internet.
The second one is quite recent, they started the construction in 2004, about the time I was starting to visit Mukdahan quite regularly. It is 1.6 km long ( the Mekong is indeed not a small river) and has two traffic lanes.
And it was not that easy to build it up. An accident happened on 22 July 2005, a crane snapped and dropped one concrete slab in the Mekong river. With a few Japanese engineers, Thai, Lao and Filipino. Killing them. I took some pictures long after that incident but the slab that fell is still visible.
In dry season
In rainy season
On the other side of the Mekong river is Savannakhet, the second largest city in Laos, after Vientiane, but well, still pretty small by Thai standards. The interesting and attractive point about this second bridge is that from Mukdahan/Savannakhet, you only have to drive about 236 km to be in Lao Bao in Vietnam, making it the shortest route to reach Vietnam from Thailand.
The road in Laos is not that well maintained, so do not expect to cover the 236 km in 2 hours but more like in 6 hours or more. But still, in the past few years, there has been quite a big influx on Vietnamese and Lao tourists in Mukdahan, resulting in quite a boom in the small city.
There is only one problem when you take your Thai car to go to Vietnam, we drive on the left in Thailand, they drive on the right in Laos and Vietnam, so except if you are British and used to doing that when you go to continental Europe with your car, you’ll find it a bit awkward (if they actually let you take your car across the border).
Some more pictures of the bridge.