Check with the local Board of Nursing since each state has different requirements and regulations. In some states, an LPN can only work as a CNA or MA if they are a certified CNA or MA.
However, many states allow LPNs to work as a CNA or MA without the certification. Note that you will still be held to the standards of your license.
The same is true if an RN was working as an LPN, they can only practice under the scope of the LPN license, but will be held to the standards of an RN.