I find that meta’s translations are very poor compared to others, at least for relatively obscure languages.

Google Translate is a good default, but LLMs are really good at translations, as there better capable at understanding context and providing culturally appropriate translations.

(I live in Cambodia where they speak Khmer)

That's a high count, but still a bit away from "Omni". Usual count is between 4k and 8k depending the source. But the first 1k might be the hardest, certainly.