The first step is to obtain a Laos visa in Bangkok. This will cost around $30.00 – $40.00 and can be obtained at almost all Travel agents.
The Train leaves Hualompong station in the evening at eight o'clock and nine o'clock. It is then a ten to twelve hour journey to Nong Kai near the border.
Then you need to take a $.75 to $1.00 baht tuk-tuk to the Friendship Bridge connecting Thailand and Laos. A ten baht bus will then take you over the border.
From here Vientiane is around 15 kilometers away. It's either a $.75 Baht songtaow or a $2.50Taxi (roughly). The Thai Embassy in Vientiane again takes 2 working days. You simply have to repeat the process to get back to Bangkok.
Thailand to Laos
Mekong Ferry Mukdaharn – Savannakhet
Laos visas are required.
Laos to Thailand
Mekong Ferry Savannakhet – Muhdaharn
This is an International Checkpoint