Having a separate log for every ICMP packet that is part of the same ping tracked "session" is not generally something that you want; keep in mind that setting Accounting on the rule matching the ping traffic would give you byte and packet totals for the duration of the ping session.
However you could make sure that echo-request is freely allowed by your Access Control policy, then in Threat Prevention create a custom Indicator for ABOT that will match the ping traffic you want (by IP address or whatever) and have it issue a log (and even grab a packet capture) for each ICMP packet. However this could substantially increase the logging load on the firewall and I'd not recommend trying it.
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