What makes a good teacher? In a county like Thailand where you can teach kids with zero qualifications or experience, I'd say being normal is the biggest thing. Having a good work ethic and integrity will enable you to learn as you go, try your hardest and simply do the best you can do.
But let's get away from the teacher, and focus on their surroundings. Let's look at a good boss. A good boss is responsible for finding the best teachers hers/his budget allows. You can only work with what you have. If you take from the budget because you're a greedy boss, looking for good teachers will become increasingly harder and karma will rear its head now and again. I was given the job of finding new teachers at my old school and two of them couldn't have been better. The 3rd one turned out to be awful and was quickly replaced.
Instead of whining and moaning about this guy being a bad teacher, I took full responsibility. I told the school to employ the guy and the buck stopped with me. I got a new guy in and he was 'okay'. It was hard really. The budget was limited and their were no perks to offer. I tried to reward the two good guys as much as I could, but they quit at the end of two years because it really was a disposable job, and they were headed home anyway.
In the end, I went back home. I was in two minds when leaving and this swayed me. The final straw was telling the new guy that it was a 12 month contract when really it wasn't. It was 12 months if the school wanted to retain you and you wanted to continue another year. If you wanted to go or the school wanted you gone, it was 10 months.
Lying to the guy didn't sit well with me at all and I really felt like a scumbag. Fortunately, he left after four months. I decided that it wasn't for me. Loved my teaching, but hated having to find new teachers. It takes a certain kind of person in this environment to lie and not give relevant information just to get someone in the door. That really isn't me.
I left early in 2016 and it seemed to be getting so hard to find good teachers. As I told my school when they complained about wanting good teachers, "good teachers are not obliged to come and work for you". Basically 'pay up or shut up'.
My advice to any schools in the current climate is, if you find a good teacher, hold onto them for dear life. I fear it's becoming near impossible at a TEFL level now in Thailand to find new good ones.