Myanmar -Thailand Bridge in Mea Sai
If we intend to cross border by river to Loas from northern Thailand, then we can use Mekong River from Chiang Kong (Thailand) to Huay Xai (Laos). Huay Xai town in Laos is just opposite of Chiang Kong, Thailand and is just a mere 5 mins crossing by boat.
From Vientiane Laos cross border to NongKhai (Thailand) you have to take the friendship bridge open from 6.00am to 10.00 pm to cross. Towards south from Vientiane to Thakek you can also cross the border.
From Thakek, Laos cross to Nakhon Phanom (Thailand), you have to take a boat at the Mekong river. If you wish to proceed south to visit Savannakhet Laos, there you can take the second friendship bridge to cross border to Mukdahan (Thailand).
Along the whole journey from north to south you don't have to worry about border crossing. From Laos to Thailand or from Thailand to Laos. Most of the states in Laos, you can find a border crossing. Towards the most southern part of Laos you can easily find a border crossing, there is from Pakse to Ubom Radchathani (Thailand). Here you have to use Mekong river bridge.
If you wish to go to Cambodia, an easy overland passage from 4000 Island, Pakse Laos we can cross from here. There you will reach Don Crorlor (Cambodia).