i'm not sure regarding the pin number
but keep in mind that each withdrawal they will charge you additional fee + admin charge by the carrier which you withdraw from

Hmm interesting. I was able to withdraw cash with a 4-digit PIN card in Malaysia but haven't tried the other way round. 

Apologies for the late entry.
I'm afraid there's no way to circumnavigate this problem. I agree calling the local foreign bank or your bank's CS would not help much as highly likely they don't know it themselves unless they have experienced it before. You still need to look for ATMs which accept 4 digit PINs. One possibility is to use an international brand debit cards in the likes of Citibank, SCB, etc and use it at another Citibank ATM (if you are using Citibank and likewise for other cards) - in such cases the ATM will ask you to input 6 digit although the local system is 4 digit only.

Alternatively, you need to walk into the foreign bank itself with your passport and attempt to withdraw cash from your debit card manually.

Note that not necessarily the second option would work (I have never done the second approach myself). While all banks (all over the world) are supposed to support this method, a few times I have noticed foreign tourists in Malaysia being asked to use the ATM instead of using the counters/tellers in our local banks.

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Added on September 4, 2011, 1:11 pm

Highly likely not to work because if the local system is 4 digits even the ATM's of international banks will also follow 4 digits.
I'm speaking from experience in a particular country in Asia.

CS just guessing but likely never experience this themselves.