DP expires today,how to stay a bit longer in Malaysia

If you have proof your EP is being process then no problem on the Malaysian side. Singapore would be normal immigration requirements for your nationality.

When my DP was cancelled I HAD to leave Malaysia within 4 days of the end date - I got a letter which I had to hand to immigration and it said this in my passport as well.

my employer needs to provide me with their proof of my EP application on progress. that i need to carry today goingbout ciq and woosland. and return again  later, with that letter. did i got it right?

You need proof your EP is being processed - so offer letter and anything else from the company confirming DP 10 is in progress. It will depend on the immigration officer. But check with the company their preferences as well. Its hard to advise because dont know what it says in your passport. Check it carefully, if you are still able to move about for 4 days then I am guessing you can return on your DP for a couple more days with the EP in progress.

Hopefully the company made an online application and so could provide you with a print out of the system entry and confirmation of application....... Guessing they may have dealt with issues before so will surely assist or advise.

the stamp in my passport sayss until may 26.

employer said they applied online

how long can one stay in malaysia once ep is cancelled?
How to get 1 month social visit pass once ep is cancelled?

You can apply before the EP expires. Contact immigration.

my ep is not expiring.

I am planning to resign. Will i get 1 month social visit pass automatically at the time of EP cancellation?

Or i have to initiate an application separately?

You need to contact immigration. If you are cancelling your EP it may be different rules as it implies you are leaving the country.

I have read it is possible to get a one month Tourist Pass without leaving the country, but only at the end of an EP period i.e. natural expiry.

If you are just expecting to start another job, don't forget the NOC and handle it wisely as your company can refuse to issue one, which will mean you will have to leave the country on the date of your resignation and cannot return on another type of visa.

Rule of thumb - keep things simple and don't mess with immigration. The outcome will not be good.