hi Debs
you don't need a visa if you staying less than 30 days. Remember your passport should have 6 months left on it. There is an airport tax on departure. Will need to check how much it is but isn't a great amount. Recommended vaccinations are Typhoid , polio, hepA.Malaria- I THINK you only need to worry about this if you are travelling away from the cities and coasts but others will verify this hopefully.

Also worth noting that you should keep hold of your boarding pass rather than stuff it in the seat pocket and forget about it once you're on the plane.

As of a few months ago Thai immigration ask to see it as part of the new anti-terrorism measures. (Possibly so that, hypothetically, had you blown the plane up they would have known which seat you were in presuming that you had somehow survived and made it to immigration queue.)

Whatever the reason, keep it with you and it'll speed things up when you get your visa stamp. If you dont have it, no problem, just expect lots of 'tutting' and request for tickets from the Immigration officer.

The departure tax payment to get out of Thailand is 500 Baht, which has to be paid cash at the Airport.
There is a desk after check in where you get this done.

Thanks to you all.