Q1: Will my future employer find out about my past employment without my knowledge?
Ans: The answer is no as there are Personal Data Protection Act, 2010 (PDPA) to prevent your past employment information being shared. However, it can be made possible if you have signoff the PDPA release form to your future employer. Candidates are also requested by the future employer to inform the HR dept from their past few companies with regards to the employment background check excercise. 

Q2: Who and what does the future employer usually prompted when they have come in contact with my previous employment companies?
Ans: They will usually contact the Human Resource dept of your company or the director of the company (if it is a small company without HR dept) to verify your employment history as below;
- Base salary and allowances
- Employment period
- Character and work ethics
- Resignation/termination
- Any restriction on future employment set by the previous employer
- Will your previous company reemploy you in future?

Q3: Can they check my past contribution to EPF via EPF Dept or my past employment via Human Resource Ministry (Jabatan Tenaga Kerja Malaysia)?
Ans: Fortunately no as all information from these departments are private & confidential.

Q4: Can my future employer make a request to view my EPF statement?
Ans: To view your EPF statement is no difference than to view your personal bank account statement or passbook. It is obvious your future employer has serious trust issue and I would strongly recommend for the candidate to abandon the job application.

Failing to sign off the PDPA form will definitely put a candidate in a disadvantage position and it is the right thing to do. Understand this, PDPA act 2010 is created to protect information in the present as well as the past. As I recall, there is no such practice of having employment background check in the 80s or the 90s. It is obviously a practice that gives the employer an edge over employee. However, if everyone starts by NOT signing the PDPA waived form, you will start to see a dying practice of Employment Background Check.

The same goes for handing over your "pay advice". It is a practice that does not benefits the employee in anyway. If you are really good in what you are doing, it is only natural for you to command a premium price. Do take note that your annual salary is merely an investment for the company to generates greater return over time. Do you recall all of the hardwork and time that you have to put in throughout the years? The calls that you have attended after 6.00pm, weekdays and even holiday at times. Hence, go wild on your demand if you really have what it takes.

Remember, employer already has the advantage of examining the goods sold to them, and that is known as the "probation period". They are able to terminate your employment if your performance is not up to par. Probation period alone is good enough to protect employer's best interest. They do not need to know your salary scheme from the past as to dictates your salary scheme in the future. Just look at property sales for instant, do you refer to the selling price from the past just to determine the selling price of the property sold in the future? I don't think so.

Thank you cubicc, Topace111 and sweet_pez for sharing.

However not all information is accurate. Examples:

1. Will potential employer find out about past employment?
Maybe, and they can.

If past employer practise PDPA, they will request for applicant's PDPA approval.

Sometimes past HR Manager or staff can just help you make a bad impression.
E.g.
Prospective employer: Has this person named .... work in your company before?
Past employer: Er... who? I do not recall. What do you want?

That itself shows that the applicant is not memorable or stellar person.

Did not even reach the PDPA stage.
Even if ministry investigate, cannot find evidence.
Besides how would job applicant know what was said to file report.

3. Can they check my past contribution to EPF ?
cubicc express what is stated in the law but
since the rule of law is lacking, which is why Tun M is trying to reinstate,
so it is possible for a resourceful HR Manager to get hold of such information.

I have witness this first hand. 

4: Can my future employer request to view my EPF statement?
If you do not give, then they may decide you are cannot be controlled so they rather hire someone else.
Tun M remark Khairy is a good choice for U M N O president because all the old foxes can control him.

So good idea not to lie in interview.

It's none of their business. You can ask hiring manager, how much is your salary, see if she/he answers.
Up to you if you want to reveal your EPF, salary slip, bank account, etc.
I have applied to Shell, fill up application form. No calls for interview. But I started getting spam SMS.
Is your privacy more valuable or are you more desperate for a job?
Q1: Wouldn't that trigger my current superior that I am seeking out?

If boyfriend finds out girlfriend seeing other guy, not even real dating, how you think it will be.
Surely will act out and exclude you from meetings so that you do not run away with trade secrets.
If you plan half a million ad campaign . If staff going to leave (usually work in same industry)
Would you want your plans to be in jeapordy ?

Q2: Revealing on company job grade trade secret
cubicc is right. And you see what I mean when I say
real world is not the same as laws and ideals.

So never tell your boyfriend if you seeing other guys or
allow a background check (except if in Bank or Public Trust role )

Because anyone can help you make a bad impression (as above)
...oh that girl always go hang out at water cooler.

People always remember Najib as a kleptocrat swindler, none of the good that he did.

Q3: PDPA breaching?
How can you detect?

Q4: Open for exploitation where I could impersonate other HR seeking out and get the salary details
Can happen. Depends on past employer HR and if you sign release letter.

If you don't sign, they will just hire another person.
If you sign, then I wonder will you backstab me and sell my info to highest bidder.
> As you can see, it is best to NOT approve background check unless you are taking a public interest position.
> Never a good idea to cheat and lie because they can find ways to get more info about you even with PDPA.
> There is very few good HR professionals.

Most HR I see are hired mercenaries. If boss says replace staff, they will find ways to stab staff until leave.
Do you want one HR to go talk to another HR.... I don't.

I have a great team of staff. Experience. Productive. Work on their own.
But company folks hate them because they act on their own, do not respect authority, been caught snaking.

When they were assigned to me, hard to manage as hell.
Two months later, we were to go-to-team to fix company problems.

Do a background check, people condemn them as misfits or blame them for ANYTHING.
No one appreicates the problem they solve in-the-field but me.

So cubicc is right, that employer has probation period to determine if worker is productive and can fit in.
But if they big ego and want absolute control over you.... do you want to play along or get another job?