Is there a ping monitoring function for virtual servers in Monitoring menu?

No. Ping monitoring for virtual severs is not provided in Monitoring menu.
As an alternative function, "Hypervisor Status" function is provided.

For example, “VM dead peer monitoring” shows the monitoring result from the infrastructure side that provides the virtual server instance, and the trouble caused by internal instance problems (kernel panic or OS crash) occurring while the virtual server instance is running can not be detected.
* If you want to do it by Ping, you need to do it yourself.

For details, please refer the Service Descriptions.

Monitoring
https://ecl.ntt.com/en/documents/service-descriptions/rsts/management/monitoring.html