Lao-Isan & Lao-vientian 

Lao/Isan or Lao/Vientian is Lao language.It is like the same language! 

“Lao, sometimes referred to as Laotian (ລາວ, [láːw] 'Lao' or ພາສາລາວ, [pʰáːsǎːláːw] 'Lao language'), is a Kra–Dai language of the Lao people. It is spoken in Laos, where it is the official language, as well as northeast Thailand, where it is usually referred to as Isan.

— Name, Title

Like other Tai languages, Lao is a tonal language and has a complex system of relational markers.[clarification needed] Spoken Lao is mutually intelligible with Thai and Isan,

These languages are written with slightly different scripts but are linguistically similar and effectively form a dialect continuum.[6]