Bro, in your earlier post, you said, "On another note, what if it has been specifically mentioned in the Tenancy Agreement that the Landlord has the right to lock the doors and prevent the Tenant from accessing the premises if certain rules have been broken"

Emphasis added at the end there whereby my understanding was that there were some sort of house rules for the tenant to follow. As such, my reply to that was that such rules much be detailed and the way such rule would be deemed to be breached by the tenant must also be detailed.

Now you've zoomed in and stated that if the tenant does not pay-up - you've focused on that one breach. You're not referring to 'certain rules' anymore.

So now you see why we're at crossroads,buddy? 

Well, if the tenant fails to pay up, I think that goes to the root of the tenancy agreement itself and the remedy is to elect to terminate the contract, right? Why waste time to cut utilities, etc? I don't think it is just easy to just disconnect and re-connect utilities with a mere phone call. I'm sure there would be re-connection fees as well. And what if the authorities are slow to re-connect once the tenant has paid up? Who's going to responsible for the fact that the property has no electricity/water? Wouldn't the landlord then be guilty of fulfilling his side of the bargain? Wouldn't the tenant then have a cause of action against the landlord for breach of contract?

That's why I think it would be too messy to go that way - cutting off utililities when there's unpaid rental.

Before the new owner has such rights, the vendor (and currently the reluctant landlord) first has to surrender vacant possession to the owner. As such, the duty to evict lies with the vendor. The vendor can't just terminate the utilities and say that he's no longer the owner of the property - he only ceases to be the owner once vacant posession has been handed over - and VC must obviously be without the troublesome tenants holding over. 

Technically he is still the registered owner of the property until your solicitor finalises the transfer of ownership in your favour. Legalities aside, he has the existing keys and as such, he can go in and out and deal with the fixtures and fittings as he sees fit - up until your lawyer gives you the green light and you proceed to change the locks. Up to that date, whatever in the house still belongs to him. But once you change the locks - you're considered to have taken over posession of the property as the new owner (normal vacant posession would involve the handing over of the keys to signify change of ownership). He has no right over anything left in the house by then. You can stake your claim to it by then - but most people either throw it out or donate to charity, from what I know.
The ex-owner has no right to demand a single cent from you. Do not pay him anything. In fact, it would appear that he doesn't even want the stuff in the house and this may seem like a desperate attempt to squeeze some money out of you by making these baseless threats. Perhaps he can't afford to even hire movers to remove his belongings. Go lodge a police report that he threatened you for your record purposes. Perhaps next time when you change the locks you can bring it to the attention of the police and they can send someone to accompany you to ensure that the ex-owner does not cause any problems.

The problem which you are facing is the reason why a lot of people shy away from buying houses on auction, despite the temptation of lower-than-market-rate prices of same. The hassle can be too much to bear when there is someone still occupying the premises, which is often the case.

Facing a belligerant ex-owner is one thing - there have been instances where the ex-owners completely destroy the fixtures and fittings of the house before leaving and the new owners faced a huge repair/reno bill which would be more than the savings you made when purchasing the property below the market rate. Ex-owners who literally 'paint' the wall with faeces, ex-owners who leave mysterious small puppets, miniature altars, ornaments, etc in the house. Trust me, I've heard it all.

Best if you also speak to your lawyer and see if they can assist you in any way. Perhaps send a notice of eviction to the ex-owner and see if that shakes him up a bit. Pray that he just gives up and go away in peace. 

Aiyoh that's a lot of money! Didn't you check with the management before you rented it out to do a background check to see if the owner is the type who doesn't pay maintenance in time? 15k must've accumulated over the years.

Anyway, too late for that. Let's see how to solve this.

Now, first things first - management has no right to cut off your water supply. The doctrine of 'self help' is not applicable in our country. They can't take the law into their own hands and cut off the water supply on the basis that maintenance fees has not been paid. I suggest that you first demand that they reinstate the water supply. Ask them under which law did they get the authority or right to cut off the water supply on the basis that maintenance fees has not been paid.

If they refuse to reinstate, seek legal advice to send them a legal letter, demanding that they reinstate the water supply failing which you will go to Court to obtain a Court order compelling them to do so, etc etc etc (the lawyer would know how to go about it).

Fight for your right 
Is this promise stated in the tenancy? If not, you can't harp on it anymore. Verbal promise will end up as a 'your word against my word' as he will now surely deny it.

Well, in your tenancy one of the covenants of the landlord ought to state that he will make the necessary payments with regard to maintenance. If he fails to do so, the option for you to terminate the agreement ought to be there.

If it's not there, then once again, you have no remedy.

If you feel you want to leave - and the tenancy provides for the option of early termination by way of notice - do it according to the procedure stated there. Most of the time it would be by giving 1 month's notice in writing. You can't move out without notice. How are you going to take back your deposit anyway if you just move out without giving notice? So no, you can't do it that way.

Sort out the water issue fast as that is more urgent. Good luck!