If you're considering coming to Thailand on your own to find work as an English teacher, I promise you can do it.
I have done work abroad through programs and felt limited and isolated by the experience, even though it was a good first step. I would recommend anyone who is more autonomous, especially if you have teaching experience, consider going it alone. Here are some tips to consider at each stage of the process.
Getting your TEFL/CELTA/TESOL certification
If you're able, consider taking the course in the country where you want to teach, the same city if at all possible. This will build your connections and give you a chance to get a feel for the area before you sign a contract.
Also consider what your long-term plan is when deciding what course will suit your needs; a less involved course for short-term work and a more involved one for potential career teachers.
If your are confident with your classroom management skills, online courses might satisfy the requirement while people lacking confidence may choose to take the most challenging course available. In most cases, you get what you pay for, you get out of it what you put into it, etc.
Look for jobs
There are three ways teachers generally find jobs; connections with other teachers, showing up in person at schools inquiring about work, and applying to online postings via websites like 'ajarn.com'
The pros and cons of each are as follows:
Connections with other teachers is a great way to get a job as you already have the inside scoop on the school from someone you trust (at least in theory, right?). That same upside can also be a downside if that friend interferes with meeting other people or having a chance to develop your own 'face' outside of your friendship.
This is obviously a personal judgement call but worth considering since 'face' is very important in Thailand and much of Asia. It i also worth noting that you should consider the area where the school is and try not to fall for the low-hanging fruit if it won't be a good fit in other respects.
Instant interviews are another common way that experienced teachers find jobs. It involves researching cities you would like to teach in, showing up, asking a motorbike to take you to the best schools and going into the reception area with your CV/resume to inquire about teaching positions.
It can be intimidating if you've never done it before and timing is key but this method is the best way to ensure you get fair compensation and a good sense of the school prior to signing a contract. Ideally, you go to schools just before the start of either semester when schools are most often looking to fill positions.
Some schools leave hiring to an agency, especially if they don't have enough staff with good English fluency to manage the needs of all the foreign teachers. Usually a school will tell you if they hire through an agency, but often they make exceptions if they have positions they really need to fill.
Applying to online postings is a growing method of finding jobs on your own. Perhaps, in part, because it is new, it can also be the most difficult to navigate. Applying to postings online seems very efficient, but my experience has been that many inquiries go unanswered and postings are often not an accurate representation of the job or are done by agents who will lead you to believe they are from the school. As a result, I've expanded on some important information that I recommend getting prior to agreeing to anything.
Find out what position the person you are corresponding with holds
Find out exactly where the school is if it isn't immediately clear
Ask if there are any foreign teachers or Thai teachers you could meet prior to beginning work (they can give you a sense of the typical day or any distinguishing features of the school or the general area - it is easy to sense systemic problems by interacting with the teachers).
With regards to pay, ask about base salary, housing allowance, health insurance, and whether they pay for the non-b via or work permit (it is not unusual for schools not to pay for this but, if the salary seems low, it is worth asking if they can cover that expense).
Depending on the salary, it might also be worth asking about tutoring opportunities and Saturday school as a way to increase your income.
Ask what hours you are expected to be there, if there are gate duty responsibilities, and how many teaching hours you will have.
Ask about the curriculum and the books and what is expected with regards to lesson planning. Ask about resources like copiers, projectors, craft and office supplies. See if there is a library or whether the school is open to purchasing additional books that might facilitate your teaching (the importance of this will depend on the level of the students and the school's expectations).
Ask about the policy for computer usage.
Ask for the contact information for whoever you are expected to report to and be clear on the chain of command.
Ask about the dress code (many schools wear particular colors on particular days) and whether the school provides food or beverages during the school day.
Finally, while it should go without saying, please visit the school.
It is also helpful to be familiar with Thai courtesy phrases and body language (particularly the 'wai') prior to interviewing as it will go a long way to creating a good first impression, regardless of your experience level. You can find information about this is many places but I thought this was a good summary
The last option I did not touch on is to go through an agency.
I have personally had a bad experience with my agency (in part because they did not disclose that they were an agent until after I came to the school) and would generally just advise you to use caution when considering this option.