Ăn ngay nói thật.

Eating straight speaking truth.

The meaning is be honest. This follows the pattern of combining the 2nd and 4th words together for the meaning (ngay thật / straight truth). This comes from “Ăn ngay nói thật, mọi tật mọi lành / Eating straight speaking truth, all bad all good” (i.e., be honest about your strengths and weaknesses). This is equivalent to “Open and aboveboard” (i.e., aboveboard refers to hands above the playing table).