I'm not sure what plane-spotting means technically, but if you're referring to gawking at planes other than from the terminal buildings, then yes and no.
Yes, it's possible to catch the planes during takeoff and landing from the perimeter fence. Usually we drive up to one of the emergency gates and hang around there. You can get really awesome views of the gigantic monsters of planes. Plus, the noise is really deafening, but it all adds to the experience.
The downside is that it is illegal to crowd around the emergency gates for obvious reasons. I've been chased away by police at least once, but most of the time, nobody bothers you.
![Smile Smile](/images/emoticons/classic/icon_smile.gif)
Just don't visit the gate next to the airport fire station.
Just grab a cab and get the driver to bring you to Changi Coast Road. Make sure he stays there throughout your adventure, or you'd have problems getting back to the terminal.
SQ22