Asking joining bonus at first day of employment

He can ask whatever he wants. But it is an impossible ask, not gonna happen even if you are from IIM/IIT or whatever you do. It just won’t happen. The reason is, all these payments happen in scheduled way, always follows a process. Any big organisation will not make a special case for you, unless bound by law, or unless it benefits them hugely.

He can ask. But they won't pay. Payroll is tied to a systematic process every month and company won't break the cycle for sure. But still worth asking with a legitimate reason.