Ritual and respect
Ajarn
Also written arjan or acharn
What it means
A senior teacher, a step above kru in seniority and usually applied to the person who runs the camp or who taught the trainers.
You will not usually be the one deciding who gets the title. Listen to what the Thai staff call someone and use the same word.
Getting this right matters more in traditional camps than in large foreigner-facing ones, where first names are common.