Naked short means that you short a counter that you didn't have, AND didn't cover by the end of the day and is subjected to SGX buy back. The procedure is like this
a. You sell short a counter and never cover your position by buying in at the end of the day
b. On T+3, you don't have the scripts in your CDP to deliver to the buyer, so SGX will initiate a buy in for you
c. SGX will buy at 11:30am on T+4 at 2 bids higher than the closing price of T+3 or 11:30am price of T+4, whichever is higher. That is, higher of (closing of T+3 or 11:30am price of T+4) plus another 2 bids. I remember someone saying that the bids will increase every few minutes until someone sells it to SGX. Other penalties may apply.
In other words, you're subjected to the whims of the market and you'll only know the results after 3 or 4 market days. AND DO NOT BUY BACK YOURSELF - YOU'LL JUST BE OPENING ANOTHER POSITION! Good luck to you.