Thai Tone Marks & Signs - Alt Codes & Unicode

Thai is a tonal language with five tones, but its writing system does not map marks to tones one-to-one. The four tone marks — mai ek, mai tho, mai tri and mai chattawa — combine with the consonant class of the initial letter and the type of syllable to determine the actual tone. Thai consonants fall into three classes (high, middle and low), and the same tone mark on a high-class consonant produces a different tone from the same mark on a low-class one. This means you cannot read a Thai tone from the mark alone, which is the single biggest hurdle for learners.

The two remaining marks in the table are not tone marks at all. Mai taikhu, the small mark that looks like a tiny curl, shortens the vowel of the syllable it sits on. Thanthakhat, also called karan, is the silent mark: it cancels the letter beneath it, so the letter is written but not pronounced. Thai keeps original spellings of loanwords from Sanskrit, Pali and English, and karan is what tells the reader to skip the letters that Thai phonology cannot use. The word for Saturday and many borrowed terms rely on it.

Thai script has a structural feature that trips up software regularly: it is written without spaces between words. Spaces mark phrase and sentence boundaries instead. This means word segmentation is a genuine computational problem for Thai, and it affects line breaking, search indexing and word counts. If a Thai page breaks lines in visibly wrong places, the renderer is missing Thai dictionary-based line-breaking rather than mishandling the characters.

Thai also stacks marks vertically. A syllable can carry a vowel above the consonant and a tone mark above that, giving two levels of marks over one base letter. Fonts with poor Thai support collapse or overlap these, which is a rendering fault rather than bad text. The marks are combining characters stored after the base consonant, so the storage order and the visual arrangement differ — normal for Thai, and worth remembering when cursor movement or character counts look surprising.

The final entries, paiyannoi and the repetition mark, are abbreviation devices. Paiyannoi ฯ marks a shortened word, and the doubled form ฯลฯ is the Thai equivalent of etcetera. For typing, the standard Kedmanee layout is the common choice and places the tone marks on the number row, reached with Shift. There is also the Pattachote layout, which is more efficient but rarely used. Alt codes are not practical for Thai; a proper layout or an on-screen Thai keyboard is the realistic route, and on mobile the Thai keyboard puts tone marks on a shifted layer.