"The fool" refers to foolish people. Also, "folly" and "evil" may be expressed as adjectives. Alternate translation: "For the foolish person says foolish things and his heart plans evil things" (See: [[rc://en/ta/man/translate/figs-nominaladj]] and [[rc://en/ta/man/translate/figs-abstractnouns]])
Here the foolish person is referred to by his heart to emphasize his inner thoughts. Alternate translation: "he plans evil things in his heart" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
"The hungry" refers to hungry people. They are hungry because they have empty stomachs. Alternate translation: "the hungry person have an empty stomach" (See: [[rc://en/ta/man/translate/figs-nominaladj]] and [[rc://en/ta/man/translate/figs-explicit]])
"The thirsty" refers to people who are thirsty. Alternate translation: "he causes the thirsty person to have nothing to drink" (See: [[rc://en/ta/man/translate/figs-nominaladj]])