which is the best place to stay in terms of transport, sight seen , night life , street food etc. in bangkok
Just like Don, I would choose Sukhumvit area as well if you are thinking about easy access to public transport, sightseeing, nightlife and street food. Some of the hotels to check out:
DoubleTree by Hilton Hotel Sukhumvit Bangkok
Sofitel Bangkok Sukhumvit (Opening 1st July 2011)
Pullman Bangkok Grande Sukhumvit
Another area I would look into is by the Chao Phraya River. Hotels to check out:
Anantara Riverside Bangkok Resort
Royal Orchid Sheraton Hotel & Towers
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I recommend the area of Sukhumvit Rd and between Soi 2 and Soi 23 for a hotel. There are numerous hotels in the area (in all price ranges), street food markets, nightlife in nana plazaand Soi Cowboy and surrounding areas as well as great access to public transportation that will take you all over the city easily for the rest of your adventures!
Phayathai Road area, where is the interchange between Airport train and BTS line. You can travel to old town, China Town, Siam Square, Si Lom, Sukhumvit Soi 11 and Chatuchak Weekend Market.
There are various kind of accommodations from cool budget hostels to five-star hotels. Street food shops in the alleys are nice too.