Can you drive a simi with out a trailer and no cdl?

No. With a trailer, the vehicle requires a Class A CDL to be driven legally. Without the trailer (in which case, it's known as a bobtail), you're still driving a straight truck rated at 54,000 lbs. GVWR, and you're still required to possess at least a Class B CDL to operate that.

The only time you don't need a CDL to operate a tractor-trailer or straight truck with a Gross Vehicle Weight Rating of over 26,000 lbs. is when it's a vehicle exempt from CDL licencing requirements, as it's not regulated by the Federal Motor Carrier Safety Administration. Such vehicles include recreational vehicles and motorhomes, military vehicles (when operated by military personnel in the course of their duties), registered farm vehicles (which must be operated by the farmer, their family members, or direct employees of the farmer in the course of farm-related activities), and firefighting/first response apparatus.