you can also check this easily by going in vSphere Web Client (if your host is managed by vCenter)
select your Host in Host and Cluster inventory -> Related Objects -> Virtual machines tab
this is where it will list out all the VMs in your ESXi host, along with their Actual and Provisioned Size parameters, if you see both the columns reporting same size, that means it's Thick provisioned vdisk vm. if actual size is less than provisioned size, than it's thin provisioned vdisk vm.