Thai consonant classes made simple: mid, high and low

The short answer

Thai has 44 consonant letters, and each one belongs to a class: mid, high or low. Thai calls the three groups ไตรยางศ์dtrai-yaang. The names don't describe the letter's sound or pitch. The class is a label that tells you which set of tone rules a syllable follows.

You can hear why it matters with two letters that sound the same. ข and ค are both a k with a puff of air, but ข is high class and ค is low class. So ขาkǎa (leg) has a rising tone, and คาkaa (to be stuck) has a mid tone, even though neither has a tone mark.

The good news: you only need to learn 20 letters, the 9 mid and the 11 high. Every other letter is low. Our Thai alphabet page shows all 44 with their class, and you can tap any letter to hear its name.

All 44 letters by class

Crossed out: ฃ and ฅ are no longer used. Their sounds merged with ข and ค centuries ago, and the first Thai typewriter, in the early 1890s, had no keys for them. They still count among the 44 and keep their places in the alphabet.

Many of the rarer letters, such as ฐ, ศ and ษ, turn up mainly in words borrowed from Pali and Sanskrit, like ฐานtǎan (base) and ศาลาsǎa-laa (pavilion). They follow the rules of their class like any other letter.

Why Thai has consonant classes

The classes are a fossil. When the Thai script was created, in the Sukhothai period, Thai had three tones, and it still told voiced consonants such as g, d and b apart from voiceless ones. Over the next few centuries, probably between 1300 and 1600, the voiced consonants lost their voicing, and each old tone split in two: one pitch after the old voiceless consonants, another after the old voiced ones.

The sounds changed, but the spelling didn't. So the letters still record the old difference, and the tone rules read it back:

• Low-class letters once spelled voiced sounds. ค, ท and พ were a g, a d and a b; ง, น, ม and the other sonorants were voiced then as now.
• High-class letters spelled the other voiceless sounds: the ones with a puff of air, like ข and ถ, and the fricatives, like ฝ, ส and ห. ห in front of a sonorant spelled a voiceless m, n or l, which is where the silent ห comes from.
• Mid-class letters spelled plain voiceless sounds without a puff of air, plus the "glottalised" b and d of บ and ด and the glottal stop of อ.

That's also why the oldest inscriptions get by with only two tone marks, mai ek and mai tho. Mai trii and mai jattawa came later, and they're used almost only on mid-class letters.

Mid class: nine letters

Nine letters: ก จ ฎ ฏ ด ต บ ป อ. Thai children learn them with one sentence:

ไก่ จิก เด็ก ตาย บน ปาก โอ่ง

"The chicken pecked the child to death on the rim of the jar."

That covers seven of the nine. The other two, ฎ and ฏ, are rarer twins of ด and ต, found mostly in learned words such as กฎ (rule) and ปฏิบัติ (to practise); some school versions simply add them at the end.

A sound check helps too: no mid-class letter has a puff of air. They're the plain g, j, d, dt, b and bp sounds, plus อ, the silent carrier for vowels. Mid class is also the only class that uses all four tone marks in everyday spelling, as in โต๊ะdtó (table) and ตั๋วdtǔua (ticket).

High class: eleven letters

Eleven letters: ข ฃ ฉ ฐ ถ ผ ฝ ศ ษ ส ห. The school sentence for these is about a ghost:

ผี ฝาก ถุง ข้าว สาร ให้ ฉัน

"A ghost left a bag of rice for me." ข้าวสาร is uncooked rice.

Again seven of the eleven, and they're the seven you'll read every day. The other four are easy to place: ฃ is obsolete, ฐ sounds like ถ, and ศ and ษ sound like ส. Same sound, same class.

With no tone mark, a high-class letter in a live syllable gives a rising tone: สามsǎam (three), ฝนfǒn (rain), หาhǎa (to look for). That's the easiest way to spot one by ear.

Low class: paired and single letters

The other 24 letters are low class, more than half the alphabet. You don't need a sentence to find them: if a letter isn't mid or high, it's low. But Thai schools split them into two groups, and the split matters for tones.

Paired letters (อักษรคู่): 14

Each of these has a high-class letter with the same sound today. They're the old voiced consonants that merged with their voiceless partners:

The sound column uses ThaiFlip's romanization, Paiboon+, where k, t and p are the sounds with a puff of air (our guide to Thai romanization explains why). ฑ is said d in a few words, such as บัณฑิต (graduate).

Single letters (อักษรเดี่ยว): 10

These ten have no high-class twin: ง ญ ณ น ม ย ร ล ว ฬ. They're the nasals, liquids and glides ng, y, n, m, r, l and w. Thai schools have a sentence for them too:

งู ใหญ่ นอน อยู่ ณ ริม วัด โม ฬี โลก

"A big snake is lying by Wat Moli Lok." The temple's name supplies ม, ฬ and ล. The real temple is spelled โมลี; the sentence swaps in ฬ.

Why learn this group separately? Because a single letter can't borrow a twin's tones. Instead, Thai writes a silent ห in front of eight of them, which we'll come to in a moment.

Which class? Try it

Test yourself on all 44 letters. Pick a class, and the quiz tells you why it's right or wrong, using the sentences above, and plays the word the letter is named after.

Five tones from two letters

High- and low-class letters take only two tone marks, mai ek and mai tho. With those, one class alone can't spell all five tones, but a high and a low letter with the same sound can. Here's one sound with all five:

In the first table, ค่า and ข้า are both falling: two spellings, one tone. The second table is the same trick for a single letter: น has no high-class twin, so หน, a silent ห plus น, plays the high-class part. Its low tone would be spelled หน่า, which happens not to be a word.

Silent ห and อ

ห นำ: the leading ห

Put a silent ห directly in front of a single low letter, in the same syllable, and the syllable follows high-class rules. Thai calls this ห นำ, "leading ห". Compare มาmaa (to come) with หมาmǎa (dog), and นาnaa (rice field) with หนาnǎa (thick).

Real words use it with eight letters: ง ญ น ม ย ร ล ว. ณ and ฬ are single letters too, but no word starts with หณ or หฬ. You'll meet it all the time: เหงาngǎo (lonely), หรือrʉ̌ʉ (or), หวานwǎan (sweet), แหวนwɛ̌ɛn (ring) and the words below.

อ นำ: four words

In exactly four words, a silent อ before ย makes the syllable follow mid-class rules: อย่า (don't), อยู่ (to be at), อย่าง (kind, way) and อยาก (to want). Thai children remember them as one phrase, อย่าอยู่อย่างอยาก, roughly "don't live in want". With mai ek, mid class gives a low tone, so อยู่yùu is low, not falling. Our guide to saying "don't" in Thai has more on อย่า.

Leading letters and clusters

The same idea works across two syllables. When a mid- or high-class letter comes right before a single low letter with no vowel between them, the first letter gets a short a, and the second syllable follows the first letter's class, as if a silent ห were there. Thai calls this อักษรนำ, a "leading letter".

So ขนมkà-nǒm is read ขะ-หนม: นม on its own is นมnom (milk), mid tone, but in ขนม it's rising, because ข leads it. The Royal Institute dictionary writes the reading of ขนม as ขะหฺนม, with the silent ห spelled out. A few words don't follow the rule, so check new ones in a dictionary.

A cluster is different: two consonants said together at the start of one syllable, like กร, กล, คร or ขว. There, the first letter sets the class and the second one doesn't count: ขวาkwǎa (right) follows high-class ข, so it's rising, and กล้วยglûuai (banana) follows mid-class ก.

Class + syllable + mark = tone

The class is the first of three ingredients. The second is whether the syllable is live or dead. A live syllable ends in a long vowel or in m, n, ng, w or y, like มาmaa or คนkon; the vowels ำ, ไ, ใ and เ-า count as live too. A dead syllable ends in a short vowel or a k, p or t sound, like นะná, รักrák or มากmâak. The third is the tone mark, if there is one.

Put them together and every combination has one tone. Here's the whole system, with a real word for each cell:

Three patterns are worth noticing. Mid and low class sound the same in an unmarked live syllable (mid tone), so the difference only shows in dead syllables and with marks. High class is the only one that gives a rising tone without a mark. And the same mark gives different tones on different classes: mai tho makes ข้าวkâao falling but ม้าmáa high. To try every combination with a recording, use the tone decoder in our guide to Thai tones.

"Not used" means standard spelling doesn't write it. The Royal Institute's own tone drills do put mai jattawa on other classes, and casual spellings like มั๊ย bend the rule, but you won't meet it in ordinary words.

Worked examples

Here's the method on five everyday words. For each syllable: find the first consonant's class, decide whether the syllable is live or dead, check for a tone mark, then read the tone off the table.

With a tone mark, live or dead doesn't matter: the mark decides. That's why ค่ะ and คะ, the polite particles women use, differ: ค่ะ has mai ek on a low-class letter, so it's falling; คะ has no mark and is dead and short, so it's high.

See it for any word in the dictionary

You don't have to work every word out alone. Word pages in the ThaiFlip dictionary, on the website and in the app, have a Tones section that does exactly what the worked examples above do, one syllable at a time:

1. Consonant class. It names the class and why, for example "ข leads น" or "leading ห", and lists that class's letters with the deciding one highlighted.
2. Tone mark, if there is one.
3. Syllable ending. Live or dead, with the vowel length when it matters, or a note that the mark makes it irrelevant.
4. Result. The tone with its pitch shape and the rule as a sum, such as "High class + No tone mark + Dead syllable → Low", plus a tone chart with that cell outlined.

Words of more than one syllable get a tile for each. When a word isn't said the way it's spelled, the breakdown explains that first: the page for ขนมkà-nǒm shows why it's said ขะ-หนม, with a hidden short a and ข leading น, before it goes through each syllable. Words said with a different tone from their spelling are flagged too. Open the ขนม page to see it.

How to learn the classes

1. Learn the two sentences first. Say ไก่ จิก เด็ก ตาย บน ปาก โอ่ง and ผี ฝาก ถุง ข้าว สาร ให้ ฉัน aloud with the recordings until you can write the letters from memory.
2. Treat everything else as low. Then learn the ten single letters with the snake sentence, because eight of them take a silent ห.
3. Learn the pairs by sound. The seven sounds in the pairs table each have a high and a low way to write them. When you learn a word with one of them, notice which letter it uses.
4. Read real words and say the class. For each new word, name the class, the ending and the mark before you check the tone. It feels slow for a week or two, then becomes automatic.
5. Keep listening. The rules tell you how a written word sounds; they don't train your ear. Our guide to learning Thai puts the script and tones in the context of the whole path.

Learning the vowels alongside helps, because vowel length decides whether many syllables are live or dead. Our Thai vowels page shows every vowel with its length, and the Thai tones page has the rules as a quick reference.

Common mistakes

• Expecting the class name to be the tone. High class never gives a high tone: ขา is rising and ข่า is low. Low class gives most high tones: ค้า, รัก.
• Guessing the class from the sound. ข and ค, ส and ซ, ห and ฮ sound identical. Only the letter tells you.
• Pronouncing the silent ห. หมา sounds like มา with a rising tone. There's no h in it.
• Using the second letter of a cluster. In ขวา, ว is low class, but ข comes first, so the word is rising.
• Missing a leading letter. The นม in ขนม isn't the mid-tone นม (milk): ข leads น, so it's read หนม, with a rising tone.

ก ข ค

See the rule behind every tone.

ThaiFlip's dictionary word pages show the tone breakdown, syllable by syllable, with recordings of the word and of real example sentences.

Frequently asked questions

Recordings and example sentences come from the ThaiFlip dictionary. Spotted a mistake? Tell us and we'll check it.

Keep reading

Thai tones: how to hear, say and read all five

Thai romanization explained: RTGS, Paiboon+ and why signs say "Sukhumvit"

How to learn Thai: a step-by-step guide