Single receiver for multiple Azure Service Bus Topic subscriptions

Hi,

I have created Azure Service Bus Topic samples from the Azure Service Bus documentation, however, I want to implement a single receiver that can receive messages from different Topic/subscriptions. 

For Example Topic 1 has a Subscription "sub 1" and Topic 2 has a Subscription "sub 2". Then my receiver should be able to receive messages from both of these subscription.

I am using onMessage method for receiving messages for 1 subscription, so do I have to implement threads in order to start another onMessage to receive message from second subscription?