Admin Form fetch values from Database and keep it selected in dropdown

I have a custom module in admin, where I am display values in dropdown format something like below using addField function.

<select onchange="checkSelectedBean(this.value)" class="required-entry select" name="nic_id" id="nic_id">
<option value="-1">Please Select</option>
<option value="1_1.1">America</option>
<option value="2_2.2">China</option>
<option value="3_3.3">India</option>
<option value="4_4.4">Japan</option>
</select>

Here 4 is the ID for Japan and 4.4 is its unique value.

Now, If I select Japan as an option and save it, I have split the post value i.e. 4_4.4 and the value saved in DB is 4 which is okay. But when I edit the same record its not showing me the saved option Japan but dropdown list of all options.

I need to know how can I make Japan as selected option in dropdown, when admin edits the same record.

Right now its showing me the dropdown list only and not the saved option.

I am fetching value from my Model/Nic.php like below.

public function toOptionArray()
         {

          $nicCollection = Mage::getModel('nic/nic')->getCollection();

          $nicarray = array(array('value'=>-1, 'label'=>'Please Select'));

          foreach ($nicCollection as $nicList){

                $nicarray[] = array('value'=>$nicList['nic_id']._.$nicList['nic_cost'],'label'=>$nicList['nic_name']);
          }

          return $nicarray;

        }

Admin form to fetch selected dropdown with values

$fieldset->addField('nic_id', 'select', array(
          'label'     => Mage::helper('nic')->__('Nic'),
          'class'     => 'required-entry',
          'values'    => Mage::getModel('nic/nic')->toOptionArray(),
          'name'      => 'nic_id',
          )); 

Pls Help.

Thanks.