What's so incredible about this 4th cenrury inscription is that most the written words (Latin alphabets version) are very much intelligible to modern Astronesian language speakers for examples Malay and Indonesian (~300M), although the language were suppose to be older than the Old Malay.

As a comparison, the words from the Ireland Ogham stones from the same era (4th century) written in primitive Irish (before Old Irish) are not intelligible by the modern Irish Gaeilge speakers (~200K) [1].

If interested there is open source collection of Corpus of the Inscriptions of Campā available online [2].

[1] Ogham Stones [PDF]:

https://www.heritagecouncil.ie/content/files/Ogham-Stones.pd...

[2] Corpus of the Inscriptions of Campā (Champa):

https://isaw.nyu.edu/publications/inscriptions/campa/inscrip...