Static address has nothing to do with the bulb - assign the IP address on you router…
Thanks for your answer, but. I didn’t ever ask what I need to do with my router. If I want static address on an IP connected device then I want. I think I don’t have to explain why it is a must for me, simply it is. If you don’t know what a static IP is and/or what are the advantages (and disadvantages) of it, or if you know but don’t know what my situation is, better not to write. 
No, a reserved DHCP address is NOT a static IP address, it’s still a DHCP with it’s advantages and disadvantages and won’t fit to me. I want static, thank you. As I wrote lack of this is a showstopper for me. Still I’d be happy if Yeelight would implement as a feature in the near future, if not, I need to choose other product, it’s so simple.
What if I don’t even have a router only a separated dumb AP for IoT devices?
Well most people DO have routers… so I’d say your request is very specific… I think most manufacturers want to make configuration as simple as possible for most of the people, and most people have routers.
Most manufacturers already have static IP config for their devices (for example iRobot, Daikin, APC, Samsung, Shelly, Velux, Synology and so on), I don’t really understand why you are against it that hard. It’s a feature, which some people need -for example me-, some doesn’t. It’s not a must to use it if exists, while now it’s a must to use dhcp server. Just like I don’t need the scenes feature in the yeelight app, but I don’t care it’s there. Who wants will use it, I don’t. Ofc. I have devices which can run a dhcp server, but besides I feel really uncomfy to have it only because of light bulbs it would have real advantages too. Much easier and faster to have them if configured already with fixed ip with much less network overhead, can easily use with all type of VPN and so on. (As mentioned before I don’t like to use clouds for lot’s of reasons and bought only devices which are working perfectly without it.)
Most people doesn’t know what security is, they don’t even change the default password of their router, so we don’t need the possibility to change it?!? About the simple configuration: the mentioned ones have the possibility to use static IP with a really simple configuration and all are defaulting to DHCP for not advanced users so they just need to next-next-finish.
Any update in this matter? I’m using an app that uses discovery, but the issue is that I have 2 lights connected (same model).
My bulbs IP changes every now and then, and I can’t know which one is mine, and which one is the other one.
IP assignment is the perfect solution to that, as I’m already familier with it and using it with 3 other devices (smartphones and tv streamers).
The owner of the app doesn’t response to messages and I really don’t wanna program another app from scrach that does exactly the same as the one I’m using, just to know which light I’m controlling between the two.