Yongnan languages
Yongnan, or Yongnan Zhuang, is a dialect-bund sharing common features but not common innovations of Zhuang languages of southern China. In the classification of Pittiyaporn (2009), Yongnan is not a single language, or even a natural group, but parts of two main branches of the Tai language family (clades C, I, and M):

(clade C) Yongnan Zhuang of Chongzuo (崇左), Yongnan Zhuang of Shangsi (上思), Caolan of Vietnam*
(clade D)
(clade I) Yongnan Zhuang of Qinzhou (钦州)
(clade J)
(clade M) Wuming (Shuangqiao) dialect (武鸣)*, Yongnan Zhuang proper (邕南), Yongnan Zhuang of Long'an (隆安), Yongnan Zhuang of Fusui (扶绥)
(clade N)* Northern Tai: Saek, Bouyei, and other Northern Zhuang

* Not considered Yongnan anywhewre, nor considered Yongnan by Pittiyaporn but placed here to make the clade D monophyletic. See Tai languages for details. References

Sources
Pittayaporn, Pittayawat. 2009. The Phonology of Proto-Tai. Ph.D. dissertation. Department of Linguistics, Cornell University. Tai languages