Khmer Letter Ka

It is a Khmer consonant, not a symbol with a fixed message.

It belongs to Khmer's unaspirated k series. In a Khmer syllable it is the base, not a complete English-style "k" token. Khmer consonants carry an inherent vowel; dependent vowels may appear before, above, below, or after the base, and a subscript consonant can be joined with coeng.

where did the Khmer letter ka come from?

It evolved within a Brahmi-related South Indian script tradition.

No single inventor is documented in the consulted sources. The evidence describes gradual development from South Indian Brahmi-related forms that resemble Pallava writing; the exact source is unsettled. The earliest Cambodian records are Sanskrit, while Khmer-language writing enters the surviving inscriptional record later.

Its durable work was religious, royal, and administrative writing: temple foundations, donations, and institutional orders. The script later serves Khmer and some regional minority languages, in a religious writing environment shaped by Sanskrit and Pali. Thai and Lao are related through the wider Brahmi-derived family, but their letters and spelling rules are not interchangeable with ក.