I entered at Nong Khai a couple of weeks ago with no problems, 1 bike and 1 pillion, see this thread,Hey Matt,
I'm thinking about crossing over at the Nong Khai border into Lao in mid December (on my Thai registered bike) and going by what you said, it is doable but a bit of a hassle. Is it generally ok to cross there now? Last year I heard via GT that it was not and crossed over from Chiang Rai to Huay Xai instead with no problem. You say that Thai officers kept rejecting you but you got through eventually; is there any way I can prepare to make it easier?
Vang Vieng Via Nong Khai