Hi, I think its perfectly ok to use green laser pointer so long as we are responsible. Follow S & T guide on using it, like make sure you turn it off as soon as you hear/see any planes in the vicinity, do not point below 20 degrees altitude, do not point at anyone, etc. Alot of the things are dangerous, you just have to handle it with care. I don't think anything is more useful than green laser pointers for teaching constellations, and it is also very useful if you are teaching a person how to find a dso.
Anyway, <5mw (hopefully 4.99mw) lasers are legally allowed in the US and the modified ones are bright enough to be seen in singapore skies. I don't think it will attract any attention as long as precautions are strictly followed.