Context usually disambiguates the use of parentheses:

If parenthese indicate the chord sounded when a capo is used, as Big Mick explained, most chords should appear appear that way, in pairs--especially at the beginning of the piece.

If parentheses indicate passing chords, the chord should appear alone. Only spacing constraints would push it against another chord.

If only some chords occur in parentheses, directly following other chords, they are probably alternative chords. In other words, you'd play one or the other, but not both.

Bass notes are usually indicated by "/" notation: C7/G. So consider other possible meanings of parentheses first. If there's anything within any parentheses but letters, sharps and flats, you're clearly dealing with separate chords, not bass notes.