hay
verb

(archaic or literary) to know; to get to know; to learn
(‘hay’ + verb) to have a habit of (doing something)

adj

good, as in useful, inventive, interesting or entertaining; compare tốt (good as in high-quality, skillful or ethical)

adv

well

conj

or

thay
verb

to change; to replace
to act in place of, to act on behalf of, to act for

adv

Used as a modifier to indicate surprise.