Bahraini Bank Accounts on Leaving Country

No. They will be closed once the ID on file with the bank expires.  You can keep the card. And just throw it away after it expires.

ID expires after 4 years

By id I mean earlier of residence visa or CPR.

Residence visa will expire in 3 months. CPR Expiry Date is 2027

So after three months, banks will ask you to update the residence visa. When you don't, then your account will be frozen.  And a few months after that, closed.

Are there any official documents regarding this topic?

No.

Closest is CBB regulations for bank accounts ie valid residence.

However since the banks are not electronically linked with immigration (as is the case in Saudi), they still rely on documents being provided by account holders. So if you open an account today, the bank will only contact you on the expiry date (earliest of) passport, visa or CPR. And at that stage, they will find out.

As an example, I had cancelled my investor visa and moved to a 10 year self sponsorship visa. But forgot to update it in bank records. They told me to update the record almost a year later when the investor visa would have expired and I updated it then. If I didn't then my account would eventually have been frozen and closed over a period of months.

@XTang

Thanks for reply. Which bank was that?

My accounts in Hsbc, Citibank and standard chartered.