Unwritten vowels
Read syllables that have no separate written vowel sign.
คน, person, is written with two consonants and no vowel sign. You still hear a short o between them. Every spoken Thai syllable has a vowel, but not every vowel has a separate written sign. Two common patterns help you read these words.
When a closed syllable consists of just an initial and a final consonant, a short o is often understood between them. คน, person, ลม, wind, and จบ, to finish, follow this pattern. Then use the ordinary tone rules: the first consonant supplies the class and the final sound makes the syllable live or dead.
An unwritten short o
In another pattern, the first consonant starts a short syllable with an unwritten a, and the rest forms the next syllable. ขนม, dessert, has a short first syllable beginning with ข, then a second syllable นม with an unwritten o. Before applying this pattern, check for a true consonant cluster or a silent leading letter: ปลา and หมู each have just one syllable.
A high- or mid-class first consonant can also affect the tone rule of the following syllable when its initial is an unpaired low-class sonorant. In ขนม, น uses a high-class rule and the second syllable is rising. In สบาย, comfortable, บ keeps its own mid class. The article on leading consonants explains this distinction.
A short first syllable
Only certain consonant pairs make a true cluster. ตร does in ตรง, straight; ตล doesn't in ตลาด, market. ห and อ can also be silent leading letters rather than separate syllables: หมู, pork, has no vowel between ห and ม and is spoken as one syllable.
For an unfamiliar spelling, first look for a known cluster or a silent leading letter. Then consider whether the remaining letters form another syllable. This helps you choose between an unwritten o inside a closed syllable and a short first syllable with a. Use the recording or dictionary to check your guess.
Thai people are kind.
คน has an unwritten short o between its two consonants.
The desserts are very delicious.
ขนม and อร่อย both start with a short syllable whose vowel a is unwritten.
How are you?
This familiar greeting starts with a short syllable whose vowel isn't written.
Common mistake
Don't assume every sequence of consonant letters needs an extra vowel. อ and ว can be parts of written vowels: ของ and สวน are each one syllable. Other words have less predictable patterns: ละคร has a long vowel in its second syllable, and บริษัท starts with a long vowel. Check unfamiliar longer words in the dictionary.
Practise
Kai says
Thai has 44 consonant letters, but several letters share the same sound. Learning a new shape doesn't always mean learning a new sound.