Learning Thai can be a challenge for many Westerners due to the tonal nature of the language. There are five different tones in Thai and a simple error on the pronunciation of one tone can completely alter the meaning of the word.
For example, picture a lost tourist trying to find the way to a temple they want to visit and they stop and ask a local if the temple is near by or far away. The Thai word for far is glai and the word for near is glai. Further confusion is added when looking at the actual words as even the spelling is very similar; near ใกล้ | far ไกล. However to the Thais the tonal difference is as clear as night and day.
Trying to learn Thai from a book is particularly challenging as the tones are usually expressed in a cryptic code that only the most advanced cryptanalysis could figure out. Besides hiring a native tutor, audio podcasts and video tutorials are your best options for learning the Thai language.
One of my favortie websites for learning Thai is Learn Thai Podcast. With a clean design and easy to follow lessons Learn Thai Podcast offers a good selection of free Thai lessons done by a native speaker.