You can put a 12-inch mattress on a platform bed. Platform beds are compatible with any mattress thickness and any mattress type. Just keep in mind that platform beds are low-profile. The lowest platforms may only rise a few inches off the ground. So putting a 12-inch mattress on a platform frame will likely create a bed that’s around 15 inches high.
A low-profile bed can offer a sleek, modern look. However, those with mobility issues should use caution. A low-profile bed can be hard to get in and out of, so if you’re older or disabled, it may be best to avoid beds lower than 24 inches.