Why does my face look so fat when I laugh or smile? (photos)

You have nice volume to your cheeks which is evident when you smile. This is typically a sign of youth. If you are wanting to slim the lower face you can consider fat removal, You may consider Morphues8 treatments or FaceTite to tighten the skin. Botox will not help you with your concern.

you are a candidate for an early lift, you have sagging on the face. otherwsie you need a combination of non invasive options. start at home dermarolling (see link).

most of my younger clients use fillers to give them shaping especially on the cheeks, jawline, and chin which make the face look more slim and tight; and threads such as PDO or Instalift can build collagen and support the facial shaping and skin looseness over time, slowing down the aging process and given the face a more “snatched” look; and morpheus or pixel8 deep microneedling RF can tighten crepe skin especially on the neck and jawline and is great for long term tightening of the full face, neck and chest; its often used to give the face a slimmer more sculpted look because it tightens the skin and gives lift.  an early face lift/neck lift with or without buccal fat pad reduction can be performed as well even in younger clients if they want a different facial shape, maxillofacial surgery with bone breaking or shaving can also be done.
For facial slimming a combination of treatments are always needed.  Options include:1. Buccal fat pad removal to reduce fat on the lower face2. Factite or Renuvion/J Plasma to tighten the lower face, jawline, and chin to reduce fat and give the jawline and neck tightening and shaping.3. Botox to the masseter to reduce the muscular size of the jaw giving the face an illusion of being more slender4. Fillers to the jawline, chin, cheeks, temples and brow help to shape the face and make it more angled and defined5. early face/neck lift with platysmaplasty or maxillofacial surgery (bone shaving or implants)
6. botox/dysport/xeomin on the neck for platysmala bands and neck tightening 
Always use at home EMERAGSKIN dermarolling (see link to Emerageskin x anteageMD roller plus stem cells/hyaluronic acid ampules) and peels like emeragecosmetics enlighten, cosmelan or aerify that can be used to improve skin quality and tighten the skin while improving wrinkles, pigmentation, acne, and Melasma.
See an expert who does facial shaping with surgical and non surgical methods to get a comprehensive option.  Best, Dr. Emer.

Your face is well volumized and full. The dynamic changes that you see when smiling are created by the muscles of facial expression. It is possible that your lower face/cheek would benefit from buccal fat pad reduction to make your face more slender. Botox is not indicated.