Khmer script is the alphabet system used to write the Khmer language (the official language of Cambodia). This type is also used to write Pali in the Buddhist liturgy of Cambodia.
The Khmer script was adapted from the Pallava script, which ultimately descended from the Brahmi script, which was used in southern India and South East Asia during the 5th and 6th centuries AD. The oldest dated inscription in Khmer was found at Angkor Borei District in Takéo Province south of Phnom Penh and dates from 611. The modern Khmer script differs somewhat from precedent forms seen on the inscriptions of the ruins of Angkor. The Thai and Lao scripts are descendants of an older form of the Khmer script.
With 74 letters (including some without any current use), the Khmer alphabet of Cambodian consists of consonants and vowels. In which the vowels include dependent vowels (which can only be written in combination with a consonant or consonant cluster) and independent vowels (which are non-diacritical vowel characters that stand alone, i.e. without being attached to a consonant symbol).
This is the longest alphabet system in Indochina.