Every one of the 44 Thai consonants belongs to one of three groups, called classes: middle, high, or low. The class isn't about how the letter looksor what sound it makes — it's a tag that determines what tone a syllable gets when you read it.
Thai is a tonal language with five tones: mid, low, falling, high, and rising. The tone of any spoken syllable is decided by four things:
- The class of the syllable's initial consonant
- Whether a tone mark is written above it
- Whether the vowel is short or long
- Whether the syllable ends in a stop sound
You don't need to memorise the rules to start. Just know that the class is load-bearing — pronounce a word with the wrong tone and you might end up saying something completely different. The cards in this app colour-code each consonant by class so you build the muscle memory before the rules even enter the picture.
Mid class9 consonants
ก จ ฎ ฏ ด ต บ ป อ
Nine consonants. The simplest tone rules — most syllables that start with a mid-class consonant come out with a mid tone unless a tone mark is written. Easiest place to start.
High class11 consonants
ข ฃ ฉ ฐ ถ ผ ฝ ศ ษ ส ห
Eleven consonants. Syllables starting with a high-class consonant default to a rising tone (going up at the end). High-class can't carry every tone mark — limits which tones the syllable can take.
Low class24 consonants
ค ฅ ฆ ง ช ซ ฌ ญ ฑ ฒ ณ ท ธ น พ ฟ ภ ม ย ร ล ว ฬ ฮ
Twenty-four consonants — by far the largest class. Syllables starting with a low-class consonant default to a mid tone, but the tone-mark behaviour is different from mid class. Where most tone-rule confusion lives.
The two consonants ฃ and ฅ are obsolete — they exist in the alphabet but never appear in modern writing. They're still in your deck so you can recognise them in old texts.