Is safe to drink a beer or a non alcohol beer, if taking kolonpin0.5 mg half of 1 twice a day. I haven't drink since march and like to for Halloween?

No. No amount of alcohol is safe with a benzodiazepine such as clonazepam. "Non-alcoholic" beer often contains a very small amount of alcohol.
Congrats on. no alcohol since March! Klonopin (clonazepam) and alcohol don't mix so why don't you go with that non alcoholic beer. Yes, I know it's got just a touch but then so do twinkles. It will be safe and you can be the designated driver. Happy Halloween!