I wouldn't even worry about taking the trams at night - they are as safe as during the day. In fact I would worry more about pickpockets during the day as they will congregate around the touristy areas when lots of foriegners are in attendance.

But You have nothing to fear from the city - you didn't say what part of Asia you are from, but the pickpockets here are the same as everywhere - opportunistic but not likely to hassle you if you stay aware of what's going on.

As for taxis - they have improved alot in teh last couple of years. 2-3 years ago one of the ministries threw a fit about the ripoffs and had a lot of undercovers taking trips and then revoking licenses of drivers that tried to pull stunts. I haven't had a driver try to drive the long way somewhere in a long long time. Just make sure they turn the meter on, and never negotiate a price.

In my experience AAA taxi is very good and you would see there cars almost everywhere - but I generally just hop in whichever one is available.