The only risk in going down the overstay route for kids, is should you want to send them to school in Thailand they may need clean passports and if they will be living in Thailand long-term it makes sense for them to be legal. Otherwise overstay!
Your best bet would be to try and secure a job at an international school before you arrive in Thailand. Most such schools recruit overseas. Then they will provide you with the visa etc.
What will you be teaching? A TEFL certificate is only for teaching English. If you've never taught before, why not do a CELTA or equivalent before you go? It will be well worth it.
Jo Plummer Hi. Yes you can send an official copy. We paid for 4 copies and sent just one them. The copies are typed while the "original" is usually completed by hand and longer in length.
Immigration in Bangkok just inspected it and then handed it back. I made photocopies for them, but can't remember if they kept them. They did want to inspect the original legalised and certified one. Good luck
No, it has to be done in the UK. You can post the document from Thailand to the UK, but doing it while you're in the UK speeds up the process and avoids having to mail it from Thailand.
As soon as you get your UK Marriage certificate, get it legalised by the Legalisation Office in Milton Keynes (£30, by post), then the legalised certificate can be certified by the Thai Embassy in London (£10). The Legalisation Office will forward the document to the Embassy for you, if you include a post-paid envelope. It is MUCH easier to do all this while you're in the UK. It takes around 2 weeks.
Lucy Leibold Yes, we got our UK marriage certificate legalised in Milton Keynes and then certified by the Thai Embassy in London. The whole process took around 2 weeks, and we did it all while we were in the UK. The Legalisation Office forwarded the certificate to the Thai Embassy in London for us, but unfortunately this is not much use to you now. I would follow Tod Daniels' advice. Good luck.