A person is much more likely to achieve professional success and personal financial wellbeing by being born and raised in an affluent area of a developed economy as opposed to having been born and raised in a rural village in sub-Saharan Africa, Cambodia or Bangladesh.
So far the greatest minds on the planet have not come up with a realistic approach to eliminate this unfairness.
English has become the world's Lingua Franca giving native English speakers a major advantage in working internationally. We native English speakers are more or less the only people who can travel the world and find work without learning a foreign language.
If you were born in Finland, if you don't learn a foreign language you would be limited to communicating with a few million people. This isn't fair, but as a native English speaker, I am not complaining. Someone from Finland who desires an international career can either learn English (and/or another widely spoken language such as Spanish or Arabic), or try to make Finnish the new world's Lingua Franca.
Which strategy is more likely to lead to personal success for the individual?
To have the option or not?
As native English speakers, we have an opportunity which few other people have. This is the option to live in a foreign country by leveraging the ability to speak our native language without significant training or experience (unless one considers a 4 week TEFL course to be significant training).
If you were born Thai, you don't have this option. If a Thai wants to travel and work internationally, the person will have to learn a foreign language and much of the time, unless having very specialized skills, have to start out doing menial jobs such as cleaning or working in the fast food industry.
There is no easy path for the average Thai (I am not picking on Thais just using them as an example) straight into a "professional" position like teaching. This is not fair, and the Thai person wanting an international career can try to develop and expand the Thai language teaching industry or learn English (and/or another widely spoken language) and develop the skills and experience needed to have a professional international career.
In many cases, at least at the university level, for a Thai to become a teacher in Thailand it even requires some foreign language skills. This isn't fair, but it is the way the world is now. Maybe in 50 years speaking Chinese will be the key to having a professional international career, but for now knowing English is the key.
There is no entitlement
It would seem, some teachers confuse having the opportunity to teach one's native language in a foreign country with the right to work anywhere in the world under desired working conditions. Having the opportunity to come to Thailand to teach English because of being a native speaker of English does not come with any specific entitlements. Pay and work condition are directly related to market conditions (in case some reader's haven't been paying attention Thailand is a developing economy with slow growth and decreasing investment and trade with Western nations)
Supply and demand forces apply to workers whether they have studied the concepts or not. Teaching English in Thailand (or other countries) is generally not the path to riches, but it does provide a fantastic opportunity to explore the world, settle in a foreign land and/or do something a person can feel good about at the end of the day.
Is the fact teaching English in Thailand pays less than being an oil or gas engineer in Saudi Arabia fair? I don't know, but I know the lower level of pay is a fact. One can accept this fact or try to eliminate or neutralize the forces of supply and demand.
Are you an agent or a victim?
If a person is thinking of becoming an ESL teacher, or other occupation for that matter, there are two basic approaches one can take. A person can approach one's career as either an agent or as a victim. An agent accepts the fact the world is unfair and works to maximize his or her opportunities. The victim whines, complains and "hopes" the world changes in a way which will favor the individual. Of course there is nothing wrong with trying to change the world in our political lives, but to rely on this strategy in our personal life would not seem to be playing the odds very well.
Which approach is more likely to lead to professional success and personal satisfaction while teaching English in Thailand? Adapt yourself to your new environment or try to change Thailand (or at least make sure everyone within earshot knows of your less than positive opinions of the country and culture)?
Those choosing the victim's path can try to change the world, but with around a billion people on the planet living on less than a dollar a day it is unlikely the UN, NGOs or national governments will make improving the lives of native English speaking ESL teachers a high priority.
Life isn't fair, I suggest all of us get over it and get on with creating a successful career and happy life.