Also, a note for those with dual/multiple passports, you cannot swap passports at land borders: do it with an airport entry/exit or airport transit....
At land borders, border/immigration officers are going to ask for entry/exit between the two bordering countries in the same passport....
As tomorrow is a Thursday, no issues at all about any possible super busy crossing from Vientiane into Nong Khai such as the situation like on Friday afternoons and the weekends. A late afternoon, or even sunset crossing should be fine. But enjoying something to eat/drink in Nong Khai before boarding your train is good too!
