I'm playing this game with 2GB of ram(the ram will got consumed by other apps) and 8GB of internal memory (4GB Free) ,if you want to search my phone model it was : VIVO Y71 (2GB RAM /8GB)
It's still playable, but with little lag if your phone is in cold state, but if my VIVO start getting very hot The PUBG GAME is stuck an you can’t move, also sometimes the phone will force close the game and saying “Unfortunately PUBG MOBILE ,is using too many CPU”
But I still can play with a Mini FAN on back of my phone, i hope i can survive the update that will come in future (some update need more requirement,it will not become a problem if you are using good/HIGH-SPECS PHONE)
I hope you understand my english :v
Conclusion:
You can play it with minimal 2GB ram, but you need 3GB RAM and a powerful processor to play this game with lag free experience
Or just buy an ROG PHONE, it will run pubg without any lag or problem
Note: if you are buying ROG PHONE now the phone will cause more problem in your wallet/bank account/money)