"Membership has its privileges," runs the American Express slogan. But after Ray Parish's experience with the little green card, he doesn't feel privileged at all. Insulted would be more like it.

Parish, a 22-year-old New Yorker, was invited to apply for a card late last year with a "pre-approved" application. His first bill arrived Feb. 4, for $331; he promptly paid it. On March 4, he got his second: $204.39. He quickly paid that, too.Then, on April 5, he received his third bill, for $596. Forty-eight hours later, he got a call from a Ms. Peterson at American Express.

It was Friday, about 4:30. Peterson was polite. "We've looked in your checking account," she said, "and we're concerned because you don't seem to have enough money to pay your most recent bill."

At that moment, Parish had all of $4 in his checking account. The $596 he needed to pay his bill was stashed in an envelope. He has this little idiosyncrasy, it seems, a way of making sure he can pay his bills: Every time he makes a charge, he sets aside the cash to pay for it.

"What do you mean - `looking into my account'?" Parish asked Peterson.

"You have a checking account with National Westminster," she told him.

"Since you took the liberty of looking into that account," he replied, "you should consider that maybe I didn't intend to pay with that checking account."

"Do you have any other accounts?"

"I'm not sure I want you to know."

Peterson then asked Parish for the number of these other accounts. After he declined to provide any - none in fact existed - he was told his card would be temporarily "deactivated" until a check was received for his not-yet-overdue bill.

At Parish's request, he was switched to Peterson's supervisor, a Mr. Tartaglia.

"I wish you had called me during banking hours," Parish told him. "Then I could have transferred the funds, and my card would not need to be deactivated."

"Mr. Parish, have a nice day," said Tartag-lia, and hung up on him.

American Express initially said they didn't believe any of this. "It doesn't smack of anything that happens normally or abnormally," spokesman Gary Tobin said.

For one thing, those who like to play brinkmanship with their American Express cards - which, unlike VISA or MasterCard, is supposed to be paid off in full each month - know they have about three weeks after they get their bill before a check must be slipped in the mail. A bill paid then will still be received before the next month's is issued, and American Express will think none the worse of you.

Furthermore, Tobin said, the extent of non-payment required for card deactivation varies, "but certainly isn't three days by any stretch of the imagination." More like three months, he suggested.

When American Express checked Parish's records, its story changed. It all happened the way Parish described, the company said; the whole thing was their mistake.

Here is its interpretation: By doubling the size of his bill that third month, Parish went "out of the spending pattern." As the new cardholder was making some of his more expensive charges, the company should have warned him.

"When that purchase was called in for authorization," says Tobin, "we would have gotten him on the phone. I suspect we would have approved it, but until we received payment he couldn't have charged anything else."

Parish never was warned. He also didn't realize, even though he supplied a checking account number on his application, that this would be used for anything more than confirming his initial creditworthiness. He had, after all, been "pre-approved."

"What I found most disturbing is that they took such an interest not in whether I paid my bills but in how I paid my bills," says Parish. "I hadn't expected credit to work that way."

American Express spokesman Tobin responds that, "If you're in the credit card business, you're making somewhat arbitrary judgments about someone's ability to pay . . . We reserve the right to access (checking or other bank) accounts to ascertain whether you are able to pay the balance."

How many of American Express' 30 million cardholders realize this or read the small print on the application that warns the company "may contact these (credit) sources to update this information at any time"?

Of course, if the company satisfies itself that you can pay your bill - if Parish had had $4,000 in his checking account instead of $4 - it won't bother to call you up.

Says Parish: "I felt like I had been violated by their computer. It bothered me that while I'm sleeping at night and working here during the day, there are computers examining my life and I don't even know about it. But I learned a lesson: My life is not as private as I thought."

Three weeks ago, he received another "pre-approved" invitation to apply for an American Express card. He threw it away.