I don't live in Thailand, but we did move to Malaysia when the DDs were 9, 6 and 2.
Assuming you mean Bangkok or Phuket rather than out in the sticks somewhere, there are big expat communities all in the same boat away from home and families.
We become each others families and pull together in times of need etc (exactly as families do)
I'm a teacher too, the right international school can be a great working atmosphere after the nonsense and endless toil in UK state schools now, and will look great on his CV.
If his contract is the standard two years, it will go very fast, even if you are homesick. It takes six months to settle and get over the "holiday" feel, a year to enjoy and then six months winding down, getting ready to go back.
You'll meet some amazing people, both Thai and from all over. Great opportunities to travel etc.
But it is a stupid amount of time to get home if you need to.
My dad is ill at the moment, and I can't just pop and see him. Even a skype call takes some planning due to time differences and how he's feeling.
I've been in Asia 12 years now. DD1 is back in the UK at uni, DD2 going next year. DD3 is 14. DHs job is insecure (oil and gas) and we can't maintain our lifestyle here on my wage alone, so we are looking to go back before DD3 starts GCSEs. That is now almost as scary as when we first came out!