Bangkok does not really have a very clearly defined Downtown, but most people agree that the area around Sathorn, Siam Square and Ploenchit can be called Downtown.
Here, you find many highrise office buildings, hotels, shopping malls, restaurants and bars. As far as sightseeing is concerned, the popular choices here are Jim Thompson House, the Erawan Shrine, Kukrit’s Heritage Home, the Suan Pakkad Palace museum, Ban Kamthieng, Siam Ocean World (Southeast Asias largest aquarium) and the infamous nightlife districts Patpong, Soi Cowboy and Nana. And of course shopping in places like the Siam Paragon, Siam Discovery, Siam Center and the MBK shopping center.