I want to check for PC health in internal network using PING from external network.

Can PING package be forwarded through Mikrotik to internal network?

Yes. That's just a DST-NAT with a Protocol=icmp to get started. You can later restrict the icmp type to just 8 if you want.

Thank you very much JJCinAZ .

I have one more question, what about Wake on lan? Can we forward it too?

You should never receive that packet on an Internet connection, so by definition, no you can't "forward" it. You can get the router to send WOL packets using the /tool wol command.

The question implies some sort of WAN connectivity between locations via some sort of tunnels and there are ways to get WOL packets to move across WAN tunnels. That subject is much more complicated.