What documents do Thai nationals need and what are the procedures?

uuuh! maybe a passport  

What I mean is do they need a visa? If not then do they pay anything to get in and do they show a passport or just citizen ID?

Don't you just hate being wrong Tomy. Need a ID card. If a passport is in the possession is good but they seemed quite happy with a thai id card, which acts as a border pass.

Call the immigration office at Nong Kai for full details. I don't have the number, sorry, but it certainly wasn't a problem 3 months ago with no passport.

Presumably no passport, and no forms to fill in and no fees. Just ID?

No there are forms to fill in .The thai person needs to obtain a border pass which im not sure where they get officially .I took my girlfriend to vientianne about 1 1/2 years ago and used one of the visa shops near the bridge.They got her a border pass no problem within 30 mins and she does not have a passport only an id card.Some one on here will tell you where thais get the border pases from.

Yes they were fees i think around 200 baht but not sure as it was a while ago.

Don't you just hate being wrong Tomy

what would i know, im not thai lol,    

isn't the border pass only good for entry into Vientiene prefecture (or what ever province is directly opposite the that border if entering from elsewhere)?

If you go further into loas I think it may be worth checking out if you need a proper visa. I dunno for sure, but I suspect it may be the case. Maybe you should ask the Lao embassy.

When I used to go to Vientaine to get my visa renewed, My thai wife just had to show her ID card and the papers were filled out right there, we used to stop right where you turn off the road to the friendship bridge, where you catch the bus that takes you across,get both her entry permit and my LAO visa,Park the pickup in the sheds for a couple of days and go on across.  No prob.

The entry pass can be organised a the bus station, can't remember the cost but yes, very little. Take a couple of photos along but I think they only want one, and yes my understanding was theyty are restricted to within about 25km of Vientiane

just come back from laos with my thai g/f. if thai stays more than 3 days in laos they need a visa.

3 days is ok with border pass.for visa of 14 days they need passport.

visa is obtained at the border for $30 which is the same as farang pay.the whole procedure takes about 30 min to cross from thailand to laos including the wait for visas.