The native name of Tai Viet script and language(s)

[Eli Zaretskii via Unicode]

Could someone "in the know" please help me make the Tai Viet script
documentation in Emacs accurate?

The current short description we have is in the file
lisp/language/tai-viet.el in the Emacs source tree.  You can see it
here:

  http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/language/tai-viet.el

My concern is with the text under "sample-text" (line 40) and in the
documentation string following that (starting on line 48), which
states the name of the script and the language expressed with Tai Viet
characters.

However, that text is from long ago, before Unicode had a Tai Viet
block, so it still uses at least one PUA character, whuch I think is
incorrect.  In addition, I didn't find any place where I could
copy/paste the current accurate name of the script and at least one of
the languages that use that script.

Could someone please help me set this text straight?  Bonus points for
also telling how to say "hello" (or any similar greeting) in one of
the Tai Viet languages, so that we could add that to the etc/HELLO
file.  (I think the sample-text attempts to include such a greeting,
but again, I'm not sure it is correct.)

Thanks in advance.