Admin: Probably should post this on a Laos forum, not a member of any, apologies if this post breaches the forum rules. I heard via the bush telegraph that Thai's may enter Laos on their ID card but if staying overnight they need to enter on their passport! Can anyone confirm whether this is true or not? Cheers folks.
TLDR : Answer Summary
Thai citizens can enter Laos using their ID card for a day pass, which costs 100 Baht. However, if they plan to stay overnight, they are required to enter with a passport. A 3-day border pass can also be obtained at The Friendship Bridge in Mukdahan, but the office opens at 8:30 AM.