Interesting question, I’m a bit late to it. But today I was studying consonant clusters, so I think I can explain: ส and ว together form a consonant cluster. As the two consonants don’t really blend together they are “broken clusters”. As the second consonant is an LC1 consonant this is referred to as a musical cluster. So the short “ah” vowel is inserted between the consonants to create two syllables. For musical clusters the first consonant determines the tone for both syllables. สวัสดี becomes sà-wàt-dii High class consonant with a short vowel becomes low tone sà. High class tone rule applied to วัส becomes wàt, as it is also short vowel. Note that วัส on its own would be wát, with a high tone. I believe this is the reason why you see two low tone marks.
Create an account or sign in to comment