Upvote:1
I can't give you any specific recommendations, but both provinces do have small Cham populations, who are Muslim keep halal. So ask around for the local Cham community.
However, it'd generally difficult to keep halal even in Phnom Penh, much less in a place like Ratanakiri that's among the poorest in Cambodia. Cambodiahalatourism.com has a few listings, but it's pretty unclear if these actually serve halal food, or are just random sightseeing spots.