Teacher's Licence

It might sound a silly question, but I want to know if I can obtain a teacher's licence, even if I am not 'actively' teaching.

I live and work in Phuket, and have a WP as manager of the hotel that my Thai wife and I own.

I previously obtained a First Class Honours degree and Masters degree in electronics from the University of London.

My employment as hotel manager is more out of need to pay taxes and work towards my permanent residence, rather than any managerial requirement

So I have time on my hands and would like to work on a voluntary basis as an English (or Science/Computing etc) teacher in a local government school.

I understand the need to follow a TEFL course, (perhaps with training in the teaching of youngsters). Depending on the latest requirements, I might also need to obtain some form of Post-Grad Education certificate. Also, police clearance etc would be needed.

Assuming that I meet all the above requirements, can I apply for, (and hopefully be granted), a teacher's licence, even if I currently do not hold an offer of teaching employment?

Basically, I would like to sort out all pre-requirements so that I can quickly fill a teaching vacancy if one should arise. So my plan would be to get the teacher's licence and put this into my top drawer, to be produced when needed.

But does it work like that? Or would my licence 'expire' if not used within a certain timeframe?

Thanks for any advice.

Simon