I'm working on ethers npm package and after instantiating wallet, I'm trying to transfer some tokens to the address. but it is throwing out an error missing-signer.

Do anyone know, what mistake I might have done?

My Code :

var ethers = require('ethers');
var providers = require('ethers').providers;
var utils = require('ethers').utils;
var p = new providers.JsonRpcProvider('http://xxx.xx.xxx.xx:8545', false, 5);
ethers.Wallet.provider=p;

const contractAddress = '0x contract address here';
var contractInterface = 'contract interface here';

var data = 'wallet json from keystore';

var walletJson = JSON.stringify(data);
var wPassword='keystore account password';
ethers.Wallet.fromEncryptedWallet(walletJson, wPassword).then(function(wallet) {
    console.log("Address: " + wallet.address);    

    var address = 'adress to transfer to';
    // //var payout =  ethers.utils.parseEther('10.0');
    var payout =  1000000000;
    var contract = new ethers.Contract(contractAddress, contractInterface, wallet);

    try {
        var promise = contract.functions.transfer(address, payout);
        console.log(promise);

        promise
        .then(function(result) { 
          console.log(result); 
        })
        .catch(function(err) { 
          console.log("Promise Rejected "+ err); 
        });
    } catch (e) { 
      console.log(e); process.exit(); 
    }
}).
catch(function(err){
    console.log(err);
});

Is there anything I'm doing wrong with the account address or password(contract address)?

What might the mistake be? Any ideas?