Create two BGP ASes (Autonomous systems) in one VDOM

Yes  a typical BGP speaker is a member of only-one AS system. You might have the option for "local-as" and enable that & just for those peers.

Question,  why do you need 2x ASN?

I've only used 2x ASN from a SP role and as "temporal" when you  acquire a new network provider and need to "spook mimic" that ASN using the local-as command.

Be very careful if you use  local-as since it prepend the 2nd AS# and your route-map and route-policies could mistakenly get block or have  bad outcomes  if your not aware of what's happening ;)

Ken