khai
verb

to declare, to state, to testify
(only in compounds) to open
(only in compounds) to dredge up

adj

having the smell of urine

khui
verb

to open (something) with tools; to unpack (goods)
(figuratively) to expose; to broach; to open

開
character

(literary) chữ Hán form of khai (“to open, to start, to begin”).
Nôm form of khui (“to open, to pry open”).