laugh out of the other side of one's mouth
laugh out (of) the other side of (one's) mouth
To experience a drastic change in one's emotions or fortunes, especially from happiness to a negative emotion, often in a short span of time. A: "I thought your mother was happy that we're getting married." B: "Me too, but now, she's laughing out the other side of her mouth, and I get an angry phone call from her every day." They'll be laughing out of the other side of their mouths when they realize how much they'll have to pay in late fees.
laugh out of the other side of one's mouth
Also, laugh on the wrong side of one's mouth or face . Change from happiness to sadness, disappointment, or vexation. For example, He'll be laughing out of the other side of his mouth when he learns that he'll have to pay for the business trip he sought . [Late 1700s]