No-one expects tourist to speak the native tongue, however, a polite hello! ("sawatdee khrup" if you are a man, and "sawatdee kha" if you are a woman) will start the long process of endearing you to Thai people. If you cannot smile at the same time, then you should not be in Thailand - or anywhere else for that matter!
Thai woman welcome with closed palms - The Wai!

Some handy shopping phrases for you!
Hello =
Sawasdee (ka / krub) *
I'm just looking = Pom / chan
kae duu **
Let me have a look first =
kor pom / chan duu kon
That's pretty = Seuy dee
na (ka / krub) *
How much? = Tao rai?
Too expensive! = Pang maak na
(ka / krub!)*
Can I have a discount? =
Lod dai mai?
Do you have other colours? =
Mee see eun mai?
Do you have a smaller size? =
mee lek kwaa nee mai?
Is this made in Thailand? =
Tam nai pra ted thai rue plao?
No thanks, I'm not interested =
mai aoq (ka / krub) *
Thank you very much = Kob khun
maak - (ka / krub) *
You're so sweet! = Khun na rak maak!
* 'ka' if you are a female, 'krub' if you are a male. (Very
important. If you use both, it can lead to misunderstanding!)
** 'pom' if you a a male, 'chan' is used for both sexes
OK - So now you can go shopping with confidence