In Vietnamese poetry, there is a traditional style known as " luc. bat' " or "six eight". This not only refers to the number of syllables permitted when composing the poem, but to a general style that includes an unusual rhyme scheme as well. Luc. bat' is often associated with "ca dao" or oral folk poems/songs, though modern urban poets also enjoy experimenting with it (see The Vetiver Flower or Many by Nguyen Binh).
The rules of luc. bat' poetry:
Let's assume we are looking at a 4 line verse:
The last syllable of the first line  rhymes with the 6th syllable of the second line . The last syllable of the second line  rhymes with the last syllable of the third line . The last syllable of the third line rhymes with the sixth syllable of the fourth line .
This pattern continues for as long as the poet decides the verse will last; this decision, however, is never fixed. There are also infinite variations of the rhyme scheme, order and inversions of the six eight structure depending on the personality and education of the poet.
Uhm, sound complicated? Well it is and it isn't. Here's an example which may clarify some things:
Thuyền trăng ai chở sang Đoài
Đêm khuya mở rộng then cài cửa ra
Trăng vào, bóng nữa là ba
Với em ở trái tim ta là nhiều.
The above poem is called " Nhieu` " (Many) by Nguyen Binh
In order to experiment with a variation of the six eight rhyme scheme, I came up with an English near-equivalant I like to call "that^' cuu?" or "seven nine", because when translating Vietnamese a few extra syllables per line are often requird to expand on simplified or ambiguous vocabulary.
In my version the last word of the first line  rhymes with the seventh syllable of the second line . The last word of the second line rhymes with the last word of the fourth line . And the last word of the third line  rhymes with the seventh syllable of the fourth line . This variation is more symmetrical. Here is an example I came up with:
"Chess on Trang Tien Street"
A sidewalk cluttered with books
Two men at a crooked wood table
The lad a street shop owner
His opponent an older neighbor.
(If you don't know already, I'm a big fan of Trang Tien street!)
At the risk of sounding pretentious, I'm a fan of this new version because the ending words always have a rhyming partner, whereas in many Vietnamese six eight poems, there is much less and occasionally unpredicatble rhyme schemes. The only downside to this new version is that it is more restrictive and may cause problems when the poet needs more freedom of expression.
I've highlighted the rhymes above to reveal the relationship between the words.
Try it out yourself!