Thai is tonal language, which mean the word can change the meaning based on the pitch in with you say them. There are five tones, called mid (flat), low, high, rising (valley) and falling (hill). Changes in tones result in changes in the meaning of the words.
Ok… try to pronounce this word “khaa” with all tone.
You may find it difficult at first to pronounce all of the word in the correct tone but don’t give up.
It is so much fun; the best way to learn the tones at the beginning is keep repeating or copying the word you heard.
However, in Thai writing, the tones are quite clearly indicated by the use of Tone Marks (if you want to learn reading or writing).