Thai letter so rusi

On Kedmanee, press Shift+K; on Pattachote, press Shift+T.

Select the matching Thai keyboard layout first. These are keyboard shortcuts for so rusi; with English input active, the same keys produce something else.

Where did ษ come from?

Its roots run through Indian scripts and Old Khmer.

Thai writing developed through Old Khmer influence within the script tradition descended from Brahmi, an ancient Indian writing system. Surviving Thai writing is attested by the late 13th century. It retained letters for Pali and Sanskrit, languages that supplied Buddhist, governmental, educational, scientific and literary vocabulary.

Why does Thai still write ษ?

It preserves distinctions in spelling that pronunciation has lost. Thai ษ corresponds historically to Sanskrit ṣ, a distinct s-like consonant. Modern Thai gives ษ, ศ and ส the same initial s sound, but each word has its own spelling.

At a syllable's end, ษ is pronounced as t, with no audible release. It also belongs to the high consonant class, a letter group used with other spelling features to determine a syllable's tone.