Try this book for a good place to start when doing research on Laos. Be certain to read the Introduction to the Bibliography (pages 411-420) and see the bibliography that follows (pages 420-484):
Historical Dictionary of Laos (3rd edition) by Martin Stuart-Fox
Lanham, Md. : Scarecrow Press, 2008.
Paper Copy: Kroch Library Asia Reference (Non-Circulating) DS555.25 .S78 2008
Online Copy: https://newcatalog.library.cornell.edu/catalog/10329439
Here is an older (1991) but useful research book containing annotated title listings of major and standard information sources covering a large number of topics: