We've seen that in speaking Thai, it's important to pronounce each syllable in the proper lexical tone. We might not be understood if we do not. Next you might be wondering how to determine the correct tone. The tone of a Thai word can generally be determined from its spelling, according to a set of tone rules. The tone rules consider the specific consonants, vowels, and tone marks in a syllable to determine the tone with which the syllable must be pronounced.

Learn the Consonant Classes

If you haven't already studied the classes of the 44 Thai consonants, begin by reviewing the following chart or checking out our discussion of study approaches. One of the best methods is described in the lesson, Phonemic Approach to the Consonant Classes.

The following chart summarizes the consonant classes (the two obsolete consonants are grayed out). You can test your knowledge with the quiz, Classes of All 44 Thai Consonants.

Syllables with Tone Marks

If a syllable carries one of the four tone marks, then determining the tone is relatively simple. Two of the tone marks force a syllable to have a certain tone. In fact, these tone marks will only appear over syllables beginning with a mid-class consonant, but this extra information may just confuse matters. The important thing to remember is that always guarantees a high tone, and always guarantees a rising tone.

If one of the other two tone marks appears over a syllable, then we need to pay attention to the class of the initial consonant. Good thing we already memorized the classes of the consonants! Combining this information with the tone mark determines the lexical tone of the syllable. Refer to the following chart:

What if the syllable begins with a cluster of two consonants, like the word กว่า   /gwaaL/? Generally, if a syllable begins with an initial consonant cluster, then the class of the first consonant is used to determine the tone. The tone mark appears over the second consonant in the cluster. See Non-conforming Initial Clusters for more information on the clustered consonant tone rule.

Syllables without Tone Marks

Determining the tone of a syllable which does not carry a tone mark is somewhat more complex. First, the syllable must be classified as either live or dead. [see Consonant Endings.] This depends on its final consonant if it's a closed syllable, or the type of vowel sound (live ending vowels are marked with footnote 3 on the vowels page) if it's an open syllable. Next, you may need to know whether the syllable has a long- or short vowel.

We'll look into all of this below, where we present a comprehensive summary of the tone rules.

Overall summary of the tone rules

The table gives the lexical tone (low, mid [or "common"], rising, falling, or high) based on the initial consonant class and other considerations. When using this chart, remember that closed means that the syllable has a final consonant. Open syllables don't have a final consonant and thus end with their vowel sound. Also, the tone rules must be applied with care in certain types of Initial Consonant Clusters.

Observations

This table suggests why the mid-class consonants are so-named. In syllables without a tone mark, they bridge the low- and high-class consonants: In live syllables they act like low-class consonants, and in dead syllables they act like high-class consonants.

Tonal Composition of Thai Syllables

Now let's pivot this table to show all of the possible ways that a given lexical tone can be generated. This gives all of the twenty-two possible syllable types from a tone perspective.

Notes:
1. These syllables should always be live because otherwise the tone mark is not needed. We currently have only one word listed which is spelled with the unecessary mark: ปึ่ก   /bpeukL/. Compare with ปึก   /bpeukL/.
2. Almost always a live syllable. Exceptions: ฟู้ด  /fuutH/, โม้ก   /mo:hkH/, โน้ต  /no:htH/, etc.
3. Almost always a dead syllable. Exceptions: ปิ๊ง   /bpingH/, บ๊วย   /buayH/, กุ๊ย   /guyH/, etc.
4. In practice, always a live syllable.
5. Almost always a live syllable. Exception: อึ้บ   /eupF/.