How does the border bounce work between Thailand and Laos?

I always spend some time in Laos. It's a fantastic laid back country, and they need our money more than the Thais do.

You go to the border, stamp out of thailand, BUY the visa on arrival to Lao, stamp in and out of Lao then come back to thailand and stamp back in.

You have to stamp in&out of another country (and for most people that means buying the Lao visa on arrival at the border)

There is no amount of time you have to be out of thailand, many people just stamp in and out of the other country and come right back to thailand.