I've have experienced the same issue as yours before and somehow, it is really complicated.

For your case, did you visit your unit and check if they are there? Also, getting the locksmith to change the door lock will only further damage yourself. Why?

In our malaysia law between landlord and tenant, if you did not seek tenant consent either verbally or in written form, any attempt to cut off electricity or water, change the door lock or even access to your own unit, they can prosecuted you in court whereby they can create a story whereby their gold bar in your unit is lost due to your break in.

Also, making a police statement will not help you now.

The only thing you can do is, you make a notice which you will stick it on the door stated that you are going to stop this unit tenancy for a period of time. When you place on it, take a picture with someone as your witness and the date. After the mentioned period of time when the tenant still not returning your key and move out, you can make a police report.

With the police report, if I'm not mistaken, you will need to ask them to accompany you and "break" into your own unit.

I still remembered a link which provide a very subtle information on what you can do and what you can't do.

This is a similar info that I've found, there is another one which much more detail.

http://legal-malaysia.blogspot.my/2009/11/...f-landlord.html

I was wondering, did your unit electricity and water supply under new tenant or you? On land house, it will be best to let them register by using their name especially electricity. My previous tenant owed RM2.5k, a lot of dispute and excuses given like my unit's air conditioner is sucking too much electricity and etc.

Until you get your keys, it's hard to hold onto their promise after several instances of holding you. Until then, good luck to you then

Cheque or cash is the same. As long as the money is with you or in your bank account, then only you pass the tenant your unit's key.

From what I know, for monthly rental, it will be best for you to go there and collect personally rather than having the it being bank into your account. The reason being is that you will a glance of what has happened to your unit and listen to their rental fee delaying excuses.

Also, if the tenant is delaying the rental fee, you will need to give them a grace period for example 1 week and after that, you will need to be prudent to tell them to move out. Nowadays, there are a lot of tenants giving different excuse and one of the best way to protect yourself is to be straight forward and no hard feeling.

Good luck for your future rental then.