Joseph Diaz was doing a lot more than checking out clothes as a cashier at the trendy Tommy Hilfiger store in SoHo.

He had another employer — a gang paying him to steal credit card details from the store’s well-heeled customers so it could print phony cards with real financial info.

Diaz pleaded guilty last week in Brooklyn to federal fraud charges for his part in the thefts.

He said he would copy customers’ information onto a small device called a skimmer.

Another gang member, David Vidal, also pleaded guilty last week. Two others still face aggravated identity theft charges.