The Cambodian curry paste called kroeung is an irreplaceable ingredient in Khmer cooking and yellow kroeung is the most versatile of the curry pastes, used in many classic Cambodian dishes, especially soups and dips.
I've used samlor machou here, but you will also see it written as samlor m'chou, samlar machou, samlar m'chou, samloh machou, sam-law machou, and so on.