In modern French, the adjective "quelque" is mostly used with plural nouns, except in very formal/litterary French, and in a few set expressions like "quelqu'un" (someone), "quelque part" (somewhere) and "quelque chose" (something).

It's true that "quelque chose" and "quelques choses" are pronounced the exact same, but "quelque chose" is such a common expression that it will always be understood that way. In fact, if I wanted to say "some things" I would avoid saying "quelques choses" and go for "des choses", "quelques trucs" or "des trucs" to avoid confusion with "quelque chose".