I always stay a Novotel Sukhumvit 4 when in Bangkok. The hotel is located in busy tourist area very close to Nana Plaza (I don’t go to Nana Plaza).
Hotel staff is always very professional and extremely friendly and helpful. The hotel is clean and the rooms are nicely appointed with comfy beds and sheets. The hotel has beautiful swimming pool and bar at top of 25th floor- that alone is worth staying here for magnificent views of Bangkok. The breakfast is excellent and offers many food types: western, Asian, Indian. Great selection and again- excellent, friendly service.
Outside the hotel at night is very busy and not for the timid traveler, but I always feel safe here- even late at night. Great hotel, great value for your trip to Bangkok!