The main thing I have learned from being an English teacher in TEFL programs for about 5 years is that at the very beginning it can be a very overwhelming experience and a lot of people drop out because they feel as though they were sold a bad deal or even lies by whatever agency got them involved in this job in the first place. I would say about 50% of all the first-time teachers I have met in Thailand quit before the first term is even finished.
A lot of this comes from unrealistic expectations and especially if they were hired by an agency instead of directly by the school, they were likely told very untrue things about classroom conditions as well as the amount of support that they are going to receive from the other staff members which in most non-international-school situations is going to be almost zero support.
Images like the above are what you are likely to be shown when the agency is trying to "sell" you on the job. They present calm students that are dutifully paying attention and the classrooms have tons of extra space along with functioning whiteboards and other technology. The reality of most of the jobs is the exact opposite of this. Unless there is some sort of dire reason for it to exist most classrooms are completely packed, often to the point where there is no extra space for activities whatsoever.
In my first year of teaching I was basically thrown to the wolves and my classroom had about twice as many students in it than I would say there should be in order for anyone to get any sort of real education. They also don't tell you that Thai students attend school functions so frequently that even at a young age they are completely burned out and will utilize any opportunity to go absolutely wild. There isn't really such a thing as recess time at any of the schools I worked at and therefore the kids are either in a state of restlessness or fatigue and this is a bad mix that makes teaching almost impossible to those that have no idea what it is like to teach in this or other similar countries.
The language barrier makes things very difficult as well and I have mused many times about how I think that at a younger age it would be much more beneficial for the kids to be taught English by a Thai person even if they are not 100% correct about what it is that they are teaching. I have had situations where the kids had absolutely no idea what it was that I was saying to them or asking them to do and had to resort to pantomime on a regular basis. Also, when you cannot speak the same language as the students you will experience great difficulty in reprimanding any student that is acting up. Furthermore, some of the more naughty students may actually say nasty things right to your face knowing that you have no idea what they are saying to you. This can be very humiliating as a teacher.
All of this comes along with a very low salary as well so yeah, it's not the best. However, it does get a lot better.
For the few that make it to their second year you will find that you have some level of a strategy going into the next year and if you are smart and learned anything you will realize that classroom control is absolutely essential to being able to teach anything. Forget everything you think you know about teaching from when you were a kid because those conditions simply do not exist over here. One thing that you probably weren't cognitively aware of at the time was that your own teachers were likely imposing strict classroom control right from the start as well because Western kids are just as prone to being naughty as Asian kids are, I would say MORE likely.
In your second year you are still going to have some hiccups and your classroom will erupt into chaos every now and then, but I noticed that this happened far less frequently in my 2nd year than it did in my 1st. These days I am kind of known in the school and the kids will pipe down when my lesson starts. I no longer have to warn them or threaten them with punishments like writing lines in order to get control of them. I am known, the students have seen me in the hallway. I am not just another Jonny come lately who is only going to be here for a few weeks and can be abused with impunity.
Also, as time goes by you are going to learn what works and what doesn't and also you will realize how absolutely essential it is that you have a rock-solid lesson plan going in and perhaps have rehearsed what you are going to say out loud before the time comes. It has been my experience that the teachers that had the most trouble with the classrooms were the ones that didn't plan very well and if you give 8 year old's a chance to run wild because you have nothing planned for them, that is exactly what they are going to do.
I have been doing this for a while now and I am at the point where I am reusing lesson plans from prior years with notes taken as to what worked and what didn't. I now know what is going to work and it continues to work every year. I am only a part-time teacher now though because as I have warned many of you about over the years, I don't have the delusion that this is an actual career and my real work is doing digital nomad type stuff at home. I only teach 8-10 hours a week now which is the minimum necessary in order to have work permit.
What I am trying to say here is that if you do go into TEFL you really need to prepare for the chaos that it will initially be. The agents (if you had the misfortune of using one) almost certainly lied to you because their only objective is to get you in the job so they can get a commission, they don't actually care if you are happy there. Just remember that your classroom is going to be wild and it is only through learning to go with the flow that it will become something that you don't absolute hate. I have been doing this for years and now I don't really even mind doing it. Just like with most things, it will improve the better you get at it.