We must be careful to recognize when an initial consonant cluster invokes a sub-syllable /-ะ/. A detailed discussion can be found in the lesson, Inside a Thai Syllable: Part I. What follows is a summary.

In this role, the first consonant in the cluster is called a ‘leading consonant,’ or อักษรนำ  /akL saawnR namM/.

Also notice that when the preposed vowel portion of a straddling vowel precedes a non-conforming initial cluster, that grapheme belongs to the vowel symbol of the syllable as a whole. As such, its pronunciation is deferred until after the cluster (which contains the sub-syllable /-ะ/) is pronounced. Again, this situation is explained in more detail in Inside a Thai Syllable: Part I.

As examples of the clustered consonant tone rule, below are two lists of words from our dictionary which contain non-conforming initial consonant clusters. List (a.) shows cases in which the second consonant in the cluster is a sonorant; therefore the tone of the orthographic syllable is determined by the consonant class of the first consonant in the cluster. Also included in this list are examples of tone carry-forward, for example, when using vowel /-ahm/.

List (b.) shows cases in which the second consonant in the cluster is not a sonorant; therefore the spoken tone of the orthographic syllable is determined by the consonant class of that second consonant. Please let me know if there are corrections to these lists.

(a.) Tone is determined by the first consonant in the cluster: