Cannot save multiple checkbox value checked after a form submits on ajax load in php

I have one simple form which has: From date, To date When i click on submit i get list of car bookings on ajax load. In each row there is a checkbox to select that row and after multiple selection of row a common button is clicked to add bill on next page. Now my problem is I want to select multiple rows and again fill from date, to date and then submit form to get other list to again select other rows to add bill, now the problem is when I again submit form the old selected rows does not get saved so that i can get all rows selected all together on bill page. 1. This is ajax script

<script> $("#button").click(function(){
document.getElementById("loading").style.display = "block"; 
document.getElementById("overlay").style.opacity = '0.2';
var toDate = $("#datepicker2").val();
var fromDate = $("#datepicker").val();  
// var comp = $("#comp").val();
var dataString = 'fromDate='+ fromDate + '&toDate='+ toDate;
$.ajax({
  url: 'CloseBookingload.php',
  data:dataString,
  type: 'POST',
  success: function(result){
          // console.log(result);
           $("#load").show();
          $("#resultData").html(result);
           document.getElementById("loading").style.display = "none"; 
           document.getElementById("overlay").style.opacity = '1';
        }
      }); });</script>

This is my ajax page checkbox field after loads

 <input type="checkbox" id="checkselect" name="checkselect[]" value="<?php echo $row['car_booking_id'];?>">

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