I gotta agree with Wilso.
In Thailand, it really seems like hospitality is a religion, especially to foreign tourists.
If you need help getting around, someone will help you, and especially in the airports.
If you really want to see Thailand, DONT use one of the charter tour agencies, get yourself a local guide.
If you want to go to the beaches, then the only one I would recommend is Phuket.
It is an absolutely stunning beach (at least it was last time I was there, before the tsunami).
If I was going to Thailand for the first time, I would stay away from the beaches and go to the north, simply because everyone going to Thailand for the next few months is going to the beaches.
And the last thing you need to worry about is crime, because crime against foreign tourists in almost unheard of, and the Thai govt has no sense of humor about it.
Make sure your vaccinations are up to date, especially if you go to the northern part of the country, and STAY AWAY FROM THE SEX WORKERS.
STD's are rampant among the sex workers in Thailand.
Other then that, have a blast, and make sure you take your camera.
No matter where you go, try and see some of the old palaces and some of the Buddhist temples.
The monks are friendly and quite open to tourists.
While they are becoming more tourist oriented, some of the temples are quite beautiful.
My favorite is Wat Phra Kaeo (Temple of the Emerald Buddha), which if I remember correctly is in Bangkok, near the royal palace.
(Again, its been many years since I was there).