I actually taught mostly math and science (in English) and one year i taught all 3. Because i was in town I ended up being the go-to rescue teacher for a long time after other teachers did "a runner"

Getting a TEFL might not be required in your position and if you already have experience as an engineer and teaching english there are likely opportunities available to you that wouldn't be available to the run-of-the-mill TEFL teacher... the problem is finding them. I would imagine a good place for you to start (at least in Asia) is to look into the oil and gas industry as they are loaded and might need that sort of thing. It's worth a shot!

As far as teaching kids is concerned: If i were you you i would have a go at doing something in China (since you are already there) but to be honest i think you have much greater earning potential in doing something specialized towards engineering - i mean teaching Asian foremen or engineer-related individuals English. That is very important if they ever aspire to work on lucrative middle-eastern projects, for example.

The big money contracts for teaching kids are almost entirely located in Korea, Japan, and Taiwan. Everyone i know in this field currently makes BANK, and gets flights and accommodation paid for. I will touch base on this a bit more in the next episode, which i plan to release tomorrow :)

All the best...