Configure Always On to use secondary site as DR
Standard Edition availability groups are limited to one replica, which is clearly stated in  the documentation at Basic Always On availability groups for a single database.  So if you need to maintain a another copy, you'll need to use a different option.

Some possibilities are:  


Log shipping
Replicate the entire server at the virtual server's host layer with something like Zerto
Replicate the storage at the storage layer
Replicate the database files with a third party product that performs host-level file replication (e.g., Carbonite Double-Take).