The short version
Siam is Bangkok’s shopping and student centre, not a neighbourhood in the quiet residential sense. The value is immediate access to malls, universities, museums, offices and the central BTS interchange. The cost is crowds, event traffic, hard surfaces and a feeling that much of the street belongs to visitors and commuters.
Living beside the centre
The most liveable edges tend to be around National Stadium, Banthat Thong and the lanes towards Chulalongkorn, rather than directly above the mall cluster. These areas have more ordinary food and evening life. Siam Square itself changes character with retail cycles and events, so inspect a prospective home at both daytime and closing time.
Getting around
Siam is the interchange between the BTS Sukhumvit and Silom lines. National Stadium adds the Silom branch, while buses fill the short gaps. You can live here without a car more easily than almost anywhere in the city. Driving is an exercise in patience and parking planning.
Verdict
Siam suits a student, professional or couple who wants the city on the doorstep and does not mind paying for centrality. It is a poor fit for a family seeking a garden or for anyone who thinks a mall district feels like a local street. I would live on its edge, not in its loudest core.