I have tried Shopee and Lazada and a few online pharmacies with no luck.

You should be able to find nicotine patches in most of the bigger pharmacies around Bangkok, like Boots or Watsons. I’ve seen them stocked there before, and even some 7-Elevens carry them. If you’re not sure where to look, just ask the staff – they’re usually pretty helpful about pointing you in the right direction. It’s always nice to know there's somewhere local you can grab them when you need them!

When I lived in Pattaya, vitually every pharmacy I visited had both the nicotene patches and gum, both international brands and local, generic equivalents.