Here's the view from Marriott at Thong Lor, looking south.
Here's the view from the Hilton Sukhumvit, looking north.
Here's the view from the Holiday Inn Sukhumvit, looking west.
I prefer to stay in the Sukhumvit area rather than near the Chao Phraya river, so the view is a little different from what you can expect at the Peninsula and such.You can also stay near the Maha Nakhon to view Bangkok's new bad@ss sky scraper.