First Clue

Second Clue

Third Clue

Answer

Two words on this sign are French/English loanwords. Whenever you notice several of these diacritics, which change consonants from one series to another, on a sign, that's a pretty good clue to be on the lookout for loanwords in which "un-Khmer" sounds are represented.

Sound all the words on the sign out, and the two loan words (one's really an abbreviation) should stand out.