New Tai Lue final consonants differ from the base consonants by a
small circle at the bottom right, generally connected to the rest of
the consonant by a small stroke. There are illustrations at
http://www.unicode.org/charts/PDF/U1980.pdf .
What is the origin of this circle? I can't find any sign of it in the
sketchy Old Tai Lue materials I can find. It looks very much like the
Thai phinthu ('Pali Virama', as Unicode puts it), but is there a more
local source?
Richard.