Currently, there is only manual access to set numeric field display properties like setting thousands separators or padding with zeroes via dialog boxes on a layer's attribute table. We should enable access to these properties programmatically within the arcpy module via layer properties.
This has been marked by Kory Kramer as a Duplicate of https://community.esri.com/ideas/6759-expose-the-arcmap-layer-properties-through-arcpy. Please visit that idea to vote and comment. Thank you.