This is only pre-value.

Later on, most banks would also require proper evaluation by a certified valuer. (cost borne by you)

And these valuer, what they'd do is visit the property, check around, then try to find 3 previous transactions of the same area, then get the average value. Prepare a report to the bank. Easy money btw.

If they can't find previous transactions, they'd just adjust the value to your actual loan value. And they're PROFESSIONAL, what an irony.........

Hmm...let's say the pre-valuer informed it worth RM255K, so i proceed to buy the property at RM250K.
Thus, I will loan RM225K.

During proper evaluation, let's say the valuer informed it only worth RM220K. So how ar?
Can I still be able to loan up to RM225K?

If the bank say it worth less than what your seller quoted price then the differences you will have to cover by your own cash, they will only loan your 90% from the lesser value and not the one quoted by your seller.

Most bank are axxhole these days. During my purchasing the most they give is only 80-85%. Only CIMB offer me 90%.

If the bank say it worth less than what your seller quoted price then the differences you will have to cover by your own cash, they will only loan your 90% from the lesser value and not the one quoted by your seller.

Went to another bank, Bank M (not CIMB, CIMB gives me so-so, like other banks), and after informing Bank M, the pre-valuation prices from other banks, I told him, "if you can come up with higher pre-valuation price than those banks, I'll consider taking up loan with you."

After some days, Bank M did come up with higher pre-valuation price than the rest. Yet of course, the trick is that, Bank M's interest is a little bit higher than other banks. But then, the choices are yours to make.

Remember, the differentials that you have to pay is not just "the one quoted by your seller" - "pre-valuations price". It's "the one quoted by your seller" - "90% of pre-valuations price", like Tohsan said. Plus, the deposit 10% too.

Hmm...let's say the pre-valuer informed it worth RM255K, so i proceed to buy the property at RM250K.
Thus, I will loan RM225K.

During proper evaluation, let's say the valuer informed it only worth RM220K. So how ar?
Can I still be able to loan up to RM225K?

sometime its up to the individual officer discretion to approve the amount, it get a bit vague sometime what trigger them to approve the loan. 

Nowadays, all loan application must be refer to the HQ or regional hub for approval.
Not like the old days, when the branch manager had a great say.
However, the manager or the officer in-charge's remark/recommendation sometime does affect the end result.
Having family members or relatives as Priority Banking member can also have a certain influence.