opening times Nong Khai Imm/border

I have a friend who claimed he got a re-entry permit at Nong Khai on a Sunday.
Not wanting to go into a fight I am not sure he was mentionning the imm office or the border.
Thus can you get a re-entry permit at the boarder check point?
Is the border crossing open 24h/7days?
But he did mention they close at 4pm, so I guess he was talking imm office open on Sunday, I don't think so...