Мявчик Мявчине,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<form name="test">
<select>
<option>Српски</option>
<option>Русский</option>
<option>English</option>
</select>
<select>
<option>Tourist</option>
<option>Partners</option>
<option>Domens</option>
<option>Theatre</option>
</select>
<button type="submit">Open</button>
</form>
<script>
document.addEventListener('DOMContentLoaded', function() {
var form = document.forms.test;
form.addEventListener('submit',
function() {
var url = form[1].value + '.balkan.travel/' + ['rs','ru','en'][form[0].selectedIndex]
form.action = url;
})
});
</script>
</body>
</html>