The film is set during World War I. A "French Cambodian" contingent had heard strange stories about zombification--supposedly Angkor Wat was built by utilizing zombies--and there are tales of zombie armies easily overcoming foes. Armand Louque (Dean Jagger) brings back a priest who supposedly knows the secret of zombification, but he won't talk. So Louque and an international military contingent head to Angkor Wat on an archaeological expedition designed to discover the secret of zombification and destroy the information before zombies have a chance to "wipe out the white race".
You can stream Revolt of the Zombies (1936) free and legally on OldReel, via the Internet Archive.
Yes — it is in the public domain and can be watched and shared freely.