Loads of good advice there .... Limo is the way to go though.... pm me if you want an email address... very quick response.
One thing to add..... when you first get some local money (Baht) take the first 500 Bt note and put it into a seperate section in your wallet. You will need it to pay the departure tax as you leave.... and they only take Baht and I don't remember the machines giving change either.
check out the weather here:
http://www.weather.go.th/weather.php ...... and take an umbrella