No, this is a criminal offence in terms of the Rental Housing Act.
The landlord or Property Practitioner cannot change the locks, remove the front door or take any action which effectively locks the tenant out from the property or denies him peaceful occupation of the property without a court order.
The landlord does have legal remedy via the courts to obtain legal eviction of the tenant. It is therefore advisable to take immediate action against delinquent tenants.