notepad++ replace space and , with ,

Try to replace this regex:

\s+,

With this:

,

Another option you could do here is use a Negative Lookahead.

Find: \s+(?![^,])
Replace: 

Regular expression:

\s+            whitespace (\n, \r, \t, \f, and " ") (1 or more times)
 (?!           look ahead to see if there is not:
  [^,]         any character except: ','
 )             end of look-ahead

Or lookahead to see if there is not word characters.

Find: \s+(?!\w)
Replace:

Regular expression:

\s+            whitespace (\n, \r, \t, \f, and " ") (1 or more times)
 (?!           look ahead to see if there is not:
  \w           word characters (a-z, A-Z, 0-9, _)
 )             end of look-ahead

You could also use a Positive Lookahead here to look ahead to see if there is non-word characters.

Find: \s+(?=\W)
Replace: