instead of wasting half a day in jontien i was going to take a trip up north and do undon and nong khai with teeluk.

how many days on my visa would i get crossing into laos ? is it straight forward ? cost ? thanks

Leaving Thailand at friendship bridge in nong kai is easy. 20 b gets you a public bus across the bridge. An entry visa to Laos is $35us. From memory you fill in a form, hand over form, passport, money and picture, and they give you a visa. 

Return is just as easy, and the opposite. I think you get a standard 30 day entry stamp. However, I got a 60 day tourist visa at the Thai consulate whilst in Vientiane.  Easy, if time consuming.