Your client is a service provider.
In case of service providers, the place of supply is place where recipient is registered, in other cases the place of supply is location of registered service provider.
First of all once your client is registered, he needs to charge GST on invoice issued to his client at 18%.
Secondly, the place at which orders are received in Rajasthan where registration is already taken.
Service can be provided anywhere, you (client) need to find out place of supply for the purpose of charging IGST or otherwise.
In your case other places where goods are loaded are temporary places and you do not have any office or permanent establishment, so registration is not required.
Even rules are not clear in this regard. But in my opinion you need not have registration in different states since you already have registration at your principal place of business. However, if you have any office in other states, then you need to take registration subject to turnover limit.
Services are performed at different places and that happens in case of services, unless you have a place of business you can bill from your base state charging IGST subject to provisions of place of supply.