Á tử ngặt hoàng liên.

A mute keeping goldthread in one’s mouth.

The meaning is being unable to speak despite the pain and discomfort (i.e., bitterness). Goldthread is a bitter herb used as medicine. This is similar to “Holding one’s tongue” or “Cat got your tongue?”

Ăn như gấu ăn trăng.

Eat like a bear eating the moon.

The meaning is criticizing people who eat greedily and quickly. In the past, lunar eclipses were believed to be Asiatic black bears (aka moon bears due to the white crescent shaped patch of fur) eating the moon very greedily and quickly. This is equivalent to “Eating like a pig.”

Ăn mày đòi xôi gấc.

A beggar demands red sticky rice.

The meaning is criticizing people who are too demanding despite their positions, not knowing their place. Red sticky rice is eaten at weddings and New Year’s celebrations (i.e., food for special occasion). It comes from “Ăn mày đòi xôi gấc, ăn chực đòi bánh chưng / A beggar demands red sticky rice, a moocher demands square sticky rice cake.” This is similar to “Beggars can’t be choosers” (i.e., people in dire situations must accept whatever is given, even if it is inadequate).