@Steve *******
One time, 3 Thai friends and I went to Laos. With passports, since we were intending on heading out of Vientiane capital. In the end, we drove up to Nam Ngeum lake but stayed overnight for the 2 nights we were there in Vientiane.
Anyway, out of our party, one girl didn't realize her passport was about to expire, with just 4 months left. She was forced to get a border pass, which cost 120 Baht, took half an hour to process and allowed a stay in Vientiane prefecture only of 3 days and 2 nights, sufficient for our trip. On the Lao side another fee of something like 100 Baht was applicable. My other Thai friends didn't pay anything on either side of the border. This is further proof that a border pass just isn't worth it, except at locals only crossings or those with Myanmar, which operate a dual system, one for local travel and a secondary one, which is the same as for other foreigners, which requires a passport and visa.