Short answer. Yes. The Revised Penal Code specifically criminalizes acting as the keeper or watchman of a dive or resort where a prohibited drug is used unlawfully, and separately penalizes anyone who knowingly visits such a place, so both roles can carry criminal liability.
What the law says
Anyone who shall act as keeper or watchman of a dive or resort where any prohibited drug is used in any manner contrary to law; and 2. Any person who, not being included in the provisions of the next preceding article, shall knowingly visit any dive or resort of the character referred to above.
Revised Penal Code, Article 191 — Keeper Or Visitor Of Opium Den. Read the full provision →
Acting as keeper or watchman is itself an offense
Article 191 does not require the watchman or keeper to personally use or sell the prohibited drug at the location. The offense is defined around the role itself — anyone who acts as keeper or watchman of a dive or resort where a prohibited drug is used in a manner contrary to law falls within this provision. Standing guard, minding the premises, or otherwise functioning as the person who runs or watches over such a place is enough to trigger liability under this article, separate from whatever liability the drug users themselves may face.
The second, separate offense: knowingly visiting
The same article also penalizes a different group of people — anyone who knowingly visits a dive or resort of this character, so long as they are not already covered by liability for actually using the drug there under a separate provision. "Knowingly" is the key word: the visitor has to be aware of the nature of the place. This second clause exists to reach people who patronize or frequent such locations without themselves being caught in the act of using drugs, but who know full well what the place is.
What this means for someone hired as a watchman
If a person takes on the role of keeper or watchman of a place where a prohibited drug is being used unlawfully, Article 191 treats that role as criminal exposure in its own right — separate from any charge tied to the drug itself. Someone who is simply employed as a watchman without knowing what the establishment actually is presents a different factual situation than one who knowingly takes on the role at a place they understand to be a drug den, and that distinction can matter to how a case unfolds, but the article on its face reaches anyone who acts in that capacity. The penalty Article 191 attaches to both the keeper-or-watchman role and the knowing-visitor conduct is arresto mayor, together with a fine, applied to whichever of the two roles the person is found to have taken on.