Bangkok's secret gems??

Hi everyone,

I am visiting Bangkok from Friday through Sunday and staying at Grand Millenium Sukhumvit. I want to know if anyone has any recommendations for places that I must do. The broad categories being:
1. Nature
2. Touristy stuff
3. Markets (Local & Malls)
4. Shopping for electronics (genuine products)
5. Nightlife
6. Famous Thai Massages

Would really appreciate any feedback on all the above.

Cheers,
Sid

ps. Would love to meet people for a drink and make new friends....