Hi Steveoh, welcome on board.
If you want to earn enough money to be able to stockpile some significant savings, then a developing country is not the place to chose to be a teacher, unless you can hit the very top level of that career in say, an international school. A qualified native speaker teacher in Thailand earns around 35,000 baht per month (about 1,000 USD) which is more than adequate for living here - in fact compared with the average thai teacher's pay of about 9,000 baht, it is very good. 35,000 baht here affords a lifestyle that a TESOL teacher in Europe would not be able to enjoy. depending how you look at it, the cost of living is about one third, but a car is slightly more expensive, while a house that would cost £200,000 in the UK would cost about £30,000 here.
In Thailand, an unqualified backpacker may be lucky to earn 25,000 while a fully qualified career teacher with an MEd or a subject BA with a PGCE may command up to 100,000 baht in an elite international school, or doing full-time corporate training at 1,000 baht per hour.
I gave up a media company, a language institute, and a university post in Europe to come and settle in Thailand. I was curious, so I started on the bottom level, but within a year or so and a couple of job changes, I had quadrupled my salary.
If you have the time and don't mind spending the money, certainly do a Cambridge CELTA or a Trinity Cert. . Check any other courses very carefully, and don't hesitate to post a question on this Thailand TESOL forum
for any info about teaching in Southeast Asia (moderated by professionals).