This works, i have it downloading on my PS4 now. No payments are needed, just follow this tutorial.
*THIS IS NOT AGAINST THE TOS. PEOPLE IN ASIA GET THE BETA FOR FREE EVERY YEAR, I HAVE DONE THIS FOR BO3, AND IW.

edit: if you get any errors, try it in an incognito window and ensure you are already signed out of your pain PSN account

1. Go to this link (It's PlayStation Singapore, not some edgy website don't worry): [ Register or Signin to view external links. ]

2. Click 'Create Account' at the top of the screen.

3. Go through the process of creating the account. Make sure you select 'Singapore' as your country, language can be English; you may use fake or real information it does not matter, the only thing you will need is a postal code from Singapore. This is the first google result for Singapore postal code and works fine: '247964'

4. Once you have created the account, go back to the link in step 1: [ Register or Signin to view external links. ]

5. Click 'Try Demo', you'll see it says 'FREE'

6. Sign the account in on your PS4, and set the PS4 as a primary console for that account.

7. Go to Library > Purchased and download the WWII Beta

If you have any questions, let me know.