DataTable.Select method uses the DataColumn.Expression property. And the IN operator is listed between the allowed operators in the Expression property. So your code could be written as
DataRow[] rows = Table.Select("[ts_id] in (" + IdList + ")");
Of course this assumes that your IdList variable contains a valid string of Ids separated by commas. something like
IdList = "1,3,5,6";
If you want a DataTable as return value then you could write
DataRow[] rows = Table.Select("[ts_id] in (" + IdList + ")");
if(rows.Length > 0)
{
DataTable subTable = rows.CopyToDataTable();
......
}