The short version posted by Joe with the date 1679 (he left out a note that was with it, Ziemlich lebhaft, rather lively, which, for most of us, is superfluous anyway) is apparently the earliest. "O Du lieber Augustin" is the correct title. The "Ach" came later.
The song was a waltz at first. "The first tangible waltz tune appeared in 1679 in a popular song, "O du lieber Augustin." Waltz O du lieber
(The true Vienese waltz appeared in 1776 in the opera "Une Cosa Rara," but that is another story).

O du lieber Augustin did not appear in Vienna until about 1800, according to the more reliable references that I found. Most websites have more legend than fact about the song.
A fairly reliable version, but with the questionable "Text and Melodie: [attribution] Marx Augustin (1679)" is the following (the first three verses are the same as the "longer" version posted by Joe, but I will reproduce them and add the last verse(s):

OH, DU LIEBER AUGUSTIN

Oh, du lieber Augustin, Augustin, Augustin,
oh, du lieber Augustin, alles ist hin.
Geld ist weg, Mäd'l is weg,
alles weg, alles weg,
oh, du lieber Augustin, alles ist hin.

Oh, du lieber Augustin, Augustin, Augustin,
oh, du lieber Augustin, alles ist hin.
Rock ist weg, Stock ist weg,
Augustin liegt im Dreck,
oh, du lieber Augustin, alles ist hin.

Oh, du lieber Augustin, Augustin, Augustin,
oh, du lieber Augustin, alles ist hin.
Geld ist weg, o du Schreck,
das ist schlecht und nicht recht,
oh, du lieber Augustin, alles ist hin.

Leave off the verses about Wien and the pest in Joe's posting. They seem to have been added some time later.

Where did the verses about the plague and the stories about the unfortunate drunk sleeping with a pile of plague corpses come from? Certainly a sad change from a simple, waltz-like tune. When were they added? I couldn't find any reliable data.