No, you can't. A single online casino will only credit your account once you sign up with them. They will only credit your account with bonuses on subsequent ones. This may even lead to the banning of your account. But you can make more than one account on different virtual sites and get more than one credit in each account.
Before you do anything on PA online betting sites, please read and understand their terms and conditions.
Often, it's through checking online sites' T&Cs that one can know what the sites require and what they don't.