BrE here.
You wouldn't call someone a regular patron in normal speech.
They are a regular customer, or a client. Or they visit regularly.
If they buy something, they are a customer.
If you provide a service for them, they are a client.
A shop has customers.
Amazon has customers.
A hairdresser has clients.
A solicitor (lawyer) has clients.
Of course there is a bit of a grey area because people are buying services, but that is the general distinction. So a shop can have a regular customer and a hairdresser can have a regular client.
You would rarely talk about an individual patron. It is more of a mass term for "the people who visit the business" such as patrons at a bar. Not specific individuals who are or are not regular visitors.
You see it used in pubs and hotels because they are not shops so "customers" is not quite right, but they are certainly not professionals offering services to clients, so sometimes the term patrons is used. But that is a category of people ( people who have a right to use the parking spaces, or the toilets) not individual people.
And a jokey one, making fun of the formality if the word
A patron is usually someone who regularly gives money (or resources) to a charity or arts organisation.