Becoming fluent in Thai language is not easy, however, it is quite possible to learn some simple phrases and words that you will enjoy using, and Thais will quite happy you have tried.

Hello / Good bye

Thank you,

You're welcome

No problem

Very good

Delicious

All of the following links have audio and most are oriented for beginning level learners.

http://www.learningthai.com

http://www.seasite.niu.edu/Thai

http://www.thaisouth.com/learn_thai.php

http://www.sriwittayapaknam.ac.th/thailanguage/

http://sunsite.au.ac.th/education

http://www.travlang.com/languages

http://thaiarc.tu.ac.th/thai/introth.htm

http://www.into-asia.com/thai_language

As Thai is a tonal language - you might find it useful to listen to tapes or CDs to help you get the pronunciation right - thus the links for the audio above as well.

The time you spend picking up a few useful phrases will greatly enhance your visit to "The Land of Smiles".

Many phrase books tend to have fairly un-useful language in them: like how to purchase tickets to the opera.  It is recommend that you first learn how to order a few basic dishes and whatever you might want to drink.  These type interactions will occur much more frequently and are more likely to have misunderstandings that are bothersome - and sometimes expensive.

Good luck and enjoy!