Hop onto the BTS Sky Train (Chit Lom), ten steps from the HI & IC and head towards On Nut.

The next three stops you will encounter are :

Ploen Chit -- Nana -- Asok

I guess this covers the Sukhumvit area you are enquiring about.

No, there are no backpackers here.

The hotel is unlikely to upgrade a F&F booking unless you are a frequent guest and they use some discretion.

Have a good trip and have a look at this thread regarding immigration delays.

http://www.flyertalk.com/forum/thai-...ance-time.html