Who would you prefer to teach - young kids, teenagers or adults?
Some students are eager, some are recalcitrant; some students are delightful, some are dire. However, the good news is that to a large extent the kind of student you get is related to the kind of teacher you are.
An overview of different types of institute in Thailand and the students who go to them
At the highest echelon are the international schools. Internationals are nearly always based on the British or American curricula, and employ career teachers.