Permanent residence

Hello

I am a holder of a permanent residence card , and before my two years outside of Brasil expire .

I would like to ask whats the minimum stay I must spend in Brasil so that I dont loose that right .

Thanks

There's no minimum stay defined in the law.  As long as you come back to Brazil and pass through incoming Passport Control, you should be ok.
If your CRNM/CIE has an expiration date, you want to make sure that you're back in Brazil in time to renew it.  Letting it expire while you're abroad will cause you problems.