Ever since I started to read Khmer many aeons ago, I never managed to google myself a satisfying alphabet to refer to. So I've just drafted my own and hope it can serve you well too. If anything is missing tell me and I'll add if relevant.

Features:
• Common UN system transcription
• Regular/ Non-round style (Khmer has "bold" and "regular" glyphs, both look quite different)
• Notation of a-series and o-series vowels
• Includes independent vowels (very rare glyphs found in very common words such as "or" / "go" / "you" )
• Includes supplementary consonants (g, z, f, etc.)
• Includes colored consonants subscripts
• Includes main diacritics segregated for consonants and vowels
• Indicates dedicated computer key for each glyph
• Error-free! (Legacy glyph ordering, etc.)