Lambda https module error (succeed in postman)

Dear gurus,

I have attached a screenshot. My goal is to use lambda and make a 3rd party website request to get token. The request header/body are correct as tested in postman. But when i migrate them to lambda code (as following, it failed)

const https = require('https');

function postRequest(body) { 
   const options = {
    hostname: 'sea.bipocloud.com',
    path: '/DEMOSEA/oauth2/webapi/token',
    method: 'POST',
    port: 443, // 👈️ replace with 80 for HTTP requests
    headers: {
      // 'Content-Type': 'application/json',
      'Content-Type': 'application/x-www-form-urlencoded',
      
    },
  };

  return new Promise((resolve, reject) => {
    const req = https.request(options, res => {
      let rawData = '';
       res.on('data', chunk => {
        rawData += chunk;
      });

      res.on('end', () => {
        try {
          resolve(JSON.parse(rawData));
        } catch (err) {
          reject(new Error(err));
        }
      });
    });

    req.on('error', err => {
      reject(new Error(err));
    });

    // 👇️ write the body to the Request object
    req.write(JSON.stringify(body));
    req.end();
  });
}

exports.handler = async event => {
  try {
    
    const result = await postRequest({
      UserName: '...',
      Password: '...',
      grant_type: 'password',
      client_id: '...',
      client_secret: '...',
      serviceConnection: '...',
    });
    
    console.log('result is: 👉️', result);

    // 👇️️ response structure assume you use proxy integration with API gateway
    return {
      statusCode: 200,
      headers: {'Content-Type': 'application/json'},
      body: JSON.stringify(result),
    };
  } catch (error) {
    console.log('Error is: 👉️', error);
    return {
      statusCode: 400,
      body: error.message,
    };
  }
  
  
  
};