Single word, or phrase of two or three words, for "regular customer"?

Is there an English single term for a regular customer who, because of always buying from the same seller, acquires a discount from the seller and might also treat their relationship as that of being a friend?

In our language (Filipino), the seller calls a regular customer [a] "suki".

Patron sounds like a supporter of a cause, and habitué doesn't have the connotation of friendship. Is there a more suitable term for it in English?

pa·tron
2. A customer, especially a regular customer.
[The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000]

patron
2. (Business / Commerce) a customer of a shop, hotel, etc., esp a regular one
[Collins English Dictionary – Complete and Unabridged © HarperCollins]

Patronage -Commercial (Wikipedia)
Sometimes consumers support smaller or local businesses or corporations out of loyalty even if less expensive options exist. Their regular custom is referred to as 'patronage'.