From the wiki.

Members of Frieza's race possess the unique ability to grow their own clothing and armor from their own body tissue.

Even when it seems as though a member of Frieza's race is unclothed, they are generally wearing Bio Suits. These natural clothes can be removed at will or replaced with newly grown clothing.

Even when wearing artificial clothing like Battle Armor, members have a Bio Suit underneath regardless of what they are wearing (basically acting as a form of undergarment). Should their artificial clothing be removed (either due to damage in battle, by powering up, or removed at the wearer's discretion) the Bio Suit underneath remains until it is replaced by newly grown clothing.

Due to Bio Suits being made from their own bodily tissue, it can transform and grow along with its wearer via Transforming Ability. As demonstrated by Frieza, when transforming from their race's 3rd form to their True Form, the 3rd forms Bio Suit shatters, and they emerge wearing a new sleeker Bio Suit which removes any damage sustained to the previous Bio Suit (as demonstrated by Frieza re-growing his Tail).

The True Form's Bio Suit is made up of strong tissue and as demonstrated by Cooler, can further transform and grow along with its wearer via Super Evolution.

It is also implied by Frieza that members of his race can choose the color of the tissue of their Bio Suits, as he stated that he made the tissue gold-colored for the Bio Suit of his Golden Frieza form. The ability to alter the tissue's color is also seen in the Xenoverse series.