Reference
Tone Marks & Special Symbols
Thai is a tonal language: the same syllable said with a different pitch can mean something completely different. Four small marks written above a consonant help fix a syllable’s tone, alongside a few other symbols you will meet often in real text.
The classic example: เสือ (sǔea) is a tiger, เสื่อ (sùea) is a mat, and เสื้อ (sûea) is a shirt — three meanings separated only by tone.
The four tone marks
The tone you actually hear depends on the consonant’s class and the vowel too — but each mark has a “home” tone, shown here on a mid-class consonant so the result is clean and predictable.
Other important symbols
Not tone marks, but symbols you will see constantly once you start reading signs, names and formal text.