Postal Code in Amazon.co.jp

I have sign in with Amazon.co.jp and was stuck with the postal code. I have click the address outside Japan and put our Cambodian 5 digits postal code but it alert "Please enter a valid ZIP or Postal Code".

Can you recommend what should I do?

So.. Are you shipping from Japan to Cambodia, or are you only trying to buy something and have it shipped to Cambodia? I would just go to the cambodian version of Amazon with their website and sign up and just have it delivered. Otherwise, there should be an option to change the address on your account. I'd probably contact Amazon customer service if you're having a hard time to change the address.

Thanks for your respond, it's useful.