Try 2 Using Computed

by db_dev

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<input type="checkbox" data-bind="checked: enableElement" />
<select name="" id="select" data-bind="value:payCode, enable:enableElement">
    <option value="-1">-- Select --</option>
    <option value="82">82</option>
</select>

JavaScript

var vm = function(databaseValue) {
    var self = this;
    self.payCode = ko.observable(databaseValue);
    self.enableElement = ko.observable(databaseValue);
	
	if (databaseValue > -1) {
		self.enableElement(true);
	} else {
		self.enableElement(false);
	}
}
ko.applyBindings(new vm(82));