Road signs in Laos generally follow those used in most European countries as set out in the Vienna Convention on Road Signs and Signals. Despite this, the country itself has never signed the Vienna Convention on Road Signs and Signal. Inscriptions on traffic signs are in Lao, the national language of Laos. However, English is also used for stop and important public places such as tourist attractions, airports, railway stations, and immigration checkpoints. Both Lao and English are used on directional signage.
http://laoroadsafety.blogspot.com/p/blog-page_6.html