Materialism is a monism. It is a thesis about everything that exist being a certain kind of phenomena. Evidently, contrary to your claims above, you reject the thesis of materialism.
Presumably no one knows whether "naturalism" is a monistic thesis or not.
You need to inform yourself.
Materialism - Wikipedia
And you need to remember that philosophers use highly idiosyncratic definitions. For example Democritus's atomism is considered monistic and yet it contain multiple types of atoms, multiple properties like shape, volume, density, movement as well as space and time.
Democritus | Internet Encyclopedia of Philosophy
. From the difficulty of assigning a beginning of time, he argued the eternity of existing nature, of void space, and of motion. He supposed the atoms, which are originally similar, to be impenetrable and have a density proportionate to their volume. All motions are the result of active and passive affection. He drew a distinction between primary motion and its secondary effects, that is, impulse and reaction. This is the basis of the law of necessity, by which all things in nature are ruled. The worlds which we see -- with all their properties of immensity, resemblance, and dissimilitude -- result from the endless multiplicity of falling atoms. The human soul consists of globular atoms of fire, which impart movement to the body. Maintaining his atomic theory throughout, Democritus introduced the hypothesis of images or idols (
eidola), a kind of emanation from external objects, which make an impression on our senses, and from the influence of which he deduced sensation (
aesthesis) and thought (
noesis). He distinguished between a rude, imperfect, and therefore false perception and a true one. In the same manner, consistent with this theory, he accounted for the popular notions of Deity; partly through our incapacity to understand fully the phenomena of which we are witnesses, and partly from the impressions communicated by certain beings (
eidola) of enormous stature and resembling the human figure which inhabit the air. We know these from dreams and the causes of divination. He carried his theory into practical philosophy also, laying down that happiness consisted in an even temperament. From this he deduced his moral principles and prudential maxims. It was from Democritus that Epicurus borrowed the principal features of his philosophy.