Postbox letter from Jimmy
one red flag is a constant search for new teachers (what happened to the previous ones?).
Postbox letter from John
Sadly, many schools in Thailand prefer native speakers over Asians, even to teach math and other technical subjects.
To find the 'right' teacher, you first need to know what the 'right teacher' means.
If you're a school looking for a teacher, or a teacher looking for a school, there is someone out there for you. But if you're looking for more than a one-night stand, find the one you feel you can comfortably talk to.