Bannister's repertory grid test is helpful with thought disorder, otherwise ICD or DSM are useful heuristic devices to develop scales.

See also https://www.psycom.net/schizophrenia-test

This is difficult, and the gold standard scales are ones administered by a trained mental health professional. Some specific symptoms such as hearing voices might be possible on self completion scales, but even with these there is a significant difference between brief experiences like hearing someone say your name, hearing voices that make evaluative statements consistent with your mental state (like saying It's all hopeless or Worthless) and the more serious cases where the voices tell the person something that they didn't know or command them to do something.

Can you tell us more about why you are planning on doing this?

There are scales that explore subjective experiences and distress in people living with schizophrenia. I have developed a couple of those. E.g. The Work-related subjective experiences scale, and the work-related self-efficacy scale. But if you are seeking a diagnostic scale, subjective questionnaires are by their nature invalid for that purpose. Have a read of the DSM (4 or 5) on the nature and pathogenesis of schizophrenia and psychosis, and you will learn that it is a multi-axial disorder characterized by health history, behavior, hallucinations and cognitive symptoms; such as many types of thought disorder, as well as by negative symptoms where mental functions that should be present, are absent. Much of that can only be assessed by a qualified clinician properly trained in the assessment method. That is usually backed up by video recording so independent experts can also review the case. How is a subjective questionnaire going to detect any of that? Many people living with schizophrenia are not aware of many of their negative symptoms as symptoms, because they have not known anything else. Positive symptoms may be captured by a self-report questionnaire, but even so how would you know if they were due to a drug induced psychosis or not? If you are not seeking a diagnostic tool but are wanting to explore the cognitions and experiences for particular ethical purposes, then there is a range of recovery scales, subjective experiences scales, and self-efficacy scales; you could look at. But please do not try to diagnose severe mental illness with a subjective questionnaire as that would be scientifically inappropriate.