Best way to pass multi-select parameter list SQL

Summary:
I am working in an Oracle BI Publisher environment and ran into challenges converting a single-value parameter into a multi-select parameter, specifically for supplier/vendor filtering.

Initial Working Approach (Single Value):

Originally, I had a parameter that accepted only a single vendor name, and the query worked correctly:
AND ps.vendor_name = NVL(:P_VENDOR_NAME, ps.vendor_name)

Behavior:

If parameter is NULL, all records are returned
If parameter has a value, filtering works correctly

Change Introduced - I would like to query by multiple vendors selected

AND ps.vendor_name IN (:P_VENDOR_NAME)

Parameter Configuration:

Multiple Selection: Enabled