The paper describes the most frequent causal marker in modern Cambodian, the function word pruh. It can mark clauses describing situations the speaker views as causing some other situations or introduce noun phrases also interpreted as a cause. The paper qualifies constructions with nominal expression of cause as derived from clausal cause constructions. The marker addressed can occur in its simple form (pruh) or in a range of compound forms (pi-pruh, pruh-tae, pi-pruh-tae). Clauses or noun phrases with pruh follow consequence clauses. Where preposition of clauses or noun phrases with pruh does take place, it is invariably marked and is often accompanied by a consequence marker (tɤ:p or ba:n-ciə) in the main clause. A plausible source for pruh is the ancient Cambodian noun with the basic meaning of ‘way, mode, method’ found as early as in pre-Angkor epigraphic monuments (as of VII A.D. in roḥ / ​roḥh / ​roh forms). According to the available evidence, the prefixal, functional use of the noun as a causal marker dates back to the Middle Cambodian period (XV-XVIII centuries) when it was probably borrowed by Tai and Laotian. It is only in Modern Cambodian that pruh comes to be used as the basic neutral causal marker that carries no specific overtones like those of subjective/objective or positive/negative cause. On the other hand, pruh can mark not only the cause proper, but also express other “causal range” meanings. Similarly to the function word thvɤ:-aoj, another frequent causal marker in Cambodian, pruh can co-occur with the causative marker thvɤ:-aoj found between preposed causal clauses/noun phrases and the main clause. Notably, pruh also can co-occur with other causal markers — in the first place, with daoj-sa: and tbət.