The master or person in charge of a merchant vessel, on board of which any deserter from the Singapore Armed Forces or any visiting forces lawfully present in Singapore is concealed, shall, though ignorant of such concealment, be liable to a penaltypunished with a fine not exceeding $1,500, if he might have known of such concealment, but for some neglect of his duty as such master or person in charge, or but for some want of discipline on board of the vessel.