$JobsUsingArray  = [array](
    1 .. 3 | ForEach-Object -Process {
        Start-ThreadJob -ScriptBlock {
            [OutputType([System.String])]
            Param(
                [Parameter(Mandatory,Position=0)][string]$SomeParameter
            )
            Write-Output -InputObject $SomeParameter
        } -ArgumentList ('Hello {0}' -f $_)
    }
)
Receive-Job -Job $JobsUsingArray -Wait

Hello 1
Hello 2
Hello 3

$JobsUsingHashtable = [array](
    1 .. 3 | ForEach-Object -Process {
        Start-ThreadJob -ScriptBlock {
            [OutputType([System.String])]
            Param(
                [Parameter(Mandatory)][string]$SomeParameter
            )
            Write-Output -InputObject $SomeParameter
        } -ArgumentList @{
            'SomeParameter' = [string] 'Hello {0}' -f $_
        }
    }
)
Receive-Job -Job $JobsUsingHashtable -Wait

System.Collections.Hashtable
System.Collections.Hashtable
System.Collections.Hashtable