Glawn

Glawn or gaun (Thai กลอน) is a verse form used in the poetry and song of the Lao people; it is the most common text in traditional mor lam. It is made up of four-line stanzas, each with seven basic syllables (although sung glawn often includes extra, unstressed syllables). There is a set pattern for the tone marks to be used at various points in the stanza, plus rhyme schemes to hold the unit together. Performances of glawn are typically memorised rather than improvised.

...
Wikipedia