Also, as Andi wrote already - to be an english teacher in Thailand you must have a bachelor’s degree. That is a requierment to receive a work visa (Non-Immigrant B), which is needed to get a teaching license.
You can't "go for" either work visa or educational visa.
To get a work visa (Non-Immigrant B) you need a job first and have the necassary paperwork from the employer (plus apply for a work permit once you have the visa).
For an educational visa (Non-Immigrant ED) you must be enrolled to a school/institute/university to study in Thailand and have all the requiered paperwork from the school.
I suggest that you do some more research about different Thai visas - the web page for the Thai embassy in your home country is a good place to start.
After that, he e-mailed the embassy to ask if his financial situation could be a reason for rejection. They replied that the visa would not be approved with a sponsor.
Because of that, he contacted an agent that offered to do a new application for him, but told him that he had to wait 3 month for that.
Meanwhile he went back to Thailand, planning to apply through an agent later...
However, he never needed to use an agent. The embassy suddenly asked him to submit a new photo to his initial application and the next day it was approved (even though they had written in an e-mail that it would not be aporoved with a sponsor).
Anonym deltagare 608 further down "for the entire visa process" and "will be rejected if you are outside of the NL (the country where applied)".
This is how a visa process is supposed to be done. Prior to e-visa, the embassies even had the applicants passport during the process. The order that one is supoosed to apply and stay in the country until the visa is issued didn't change just because the application can be done online.
The fact that people ignore this, forces the embassies to do more controls, asking the applicants to submit copies of all the passport pages incl. empty ones and request interviews.
It is pretty simple - apply for the visa when you have the time for the process.