Would you really mind if I said that the Greek alphabet was credited to one Κάδμος? We know that's not true, but it doesn't change the legend (and indeed, the legend of Cadmus explicitly states that the Greek alphabet was derived from the Phoenician one...).

Both Thai and Khmer are Indic abugida scripts that derive (just like Burmese, Lao, Sinhalese, Balinese, etc.) from Brahmi. Claiming any of these scripts is one person's work is displaying abject ignorance of one of the most significant families of writing in human history.

In your personal opinion, of course