Best neighborhood and buildings in Bangkok for 1-2 month stay

My wife and I are looking to nomad for 1-2 months at the end of March. We've only lived in Chiang mai before so wondering how best to book a condo / apartment in bangkok. Airbnb and booking like pretty overpriced... is it possible to book directly with a building like it is in Chiang mai? Budget is 600-1000 usd and would like something modern on a top floor with great building amenities (gym, pool etc). Would love any recommendations.