There are many ways to learn a language. Learning Thai might be slightly more difficult than learning a language that uses the roman alphabet. Thai is written in its own script descended from Old Khmer script.

Thailand has a Romanisation of its alphabet called the Royal Thai General System of Transcription Published by The Royal Institute of Thailand. This transcription for Thai is used in government publications and road signage throughout Thailand.

Thai is a tonal language using high, medium, normal and low tones to change the sound and meaning of a word or syllable. It is this facet of the language that, while learning Thai, makes it important for the student to listen to the Thai language spoken by Thai native speakers.

When you are making your decision about how to learn Thai and what resources to use give serious consideration to a resource that includes audio.

How much listening practise do you think you would get from a Thai phrase book? Absolutely none unless you had a Thai person right beside you to pronounce the words.

When learning to speak and understand Thai it is most important that you tune your ear the tones right from the start.

As mentioned above there are many methods you can use to become proficient with Thai language. For example there are some text books that explain grammar rules in depth but fall short on pronunciation simply because teaching pronunciation is not the function of the book.