Thai is difficult (impossible?) to learn by apps or CD. Tones are everything, and it is very difficult to know if you are saying the words correctly. If you say the word using the wrong tone, it means something totally different.

I would highly recommend taking a one hour session over Skype with a Thai teacher. Most offer an introductory session with key tourist phrases. About $15 USD and you get one-on-one personal tutoring, with immediate correction of pronunciation/tones. World of difference.

One good option http://www.thaiwithjoy.com/

or just google for some other options.

My best advice for the causal / first time visitor.