Easiest way is to declare it as a global public variable


You Could Use the name and pass values to thread and retrive the value 
using

oThread.Name = strFilter
System.Threading.Thread.CurrentThread.Name

Eg. 


    Public Sub PopulateTree(Optional ByVal strFilter As String = "")
        oThread = New System.Threading.Thread(AddressOf PopulateTreeThread)
        oThread.Name = strFilter
        oThread.Start()
    End Sub


    Public Sub PopulateTreeThread()
        PopulateTree(0, tvPost.TopNode, System.Threading.Thread.CurrentThread.Name)
    End Sub


if you know something better send a mail to