In standard German (as spoken in Berlin), the word "as" (a rare loanword, e.g., in technical/anglicized contexts) would be pronounced:
[ʔas] – roughly "ahss" with a short, open 'a' (like the a in British English "father" or German "Mann") followed by a voiceless 's' (like English "s" in "see").
Breakdown:
Note: "as" is not a native German word. Native equivalents: "als" (as/when), "wie" (like/as), "so" (so/thus). If you encountered "as" in a German text, it's likely an abbreviation (e.g., a. S. = auf Seite "on page") or anglicism.