1PR4BKK where is your BF from? If he's Issan odds are he will be able to speak enough Lao to get along quite well. If he's Central Thai, Lanna, Bangkok or from the south he will not.

My BF is from Nong Khai (Issan) and we went to Lao a few years ago, he had no problem communicating but he did not feel comfortable in Lao. The one thing the Thai education system does is install a strong sense of Thai identity. He and his family essentially speak Lao as does the whole region but they don't give it much thought. They are Thai and those across the river are Lao . None of his friends or family have ever been to Lao, what the point of going there I was told.

If you BF is ThaiChi, be prepared for some incredibility pregidous remarks about Lao people.