How are preploded nasal consonants formed in some Austronesian languages?

In some Austronesian languages, particularly those found in Borneo and certain other regions, "preploded" nasal consonants are a distinct phonetic feature. These sounds are formed as nasal consonants that occur at the end of a word and are heard as /-pm/, /-tn/, and /-kng/.1

This phenomenon is distinct from "postploded" nasals, which occur between vowels and involve a nasal consonant followed by a stop that is typically very brief.1