I have teen boy who is showing a lot of interest for pot how can I make him loose interest for pot? He is like admiring stuff like marijuana, tattos, and percing, how can I make him to reject all of that, he won't obey me, any advice or comment thanks

No easy answer. Research has shown that the best preventive for drug use in teens is for there to be a strong non-drug using peer group in their school or neighborhood. Talk with people from his local school or parents association. Regular family rituals, like meals, going to activities together as a family, going to church or religious services also may help give your son alternative activities.
First . First of all let me commend you for being involved in your teen's life and noticing things that often go unnoticed (interest in drugs). Teens usually respond well to honesty. Instead of expecting him to "obey" everything you say, try taking an approach that involves you honestly telling him what your concerns are (his interest in pot) and why you think he should not use it (concern for his future, as marijuana is a gateway drug and can lead to use of more harmful drugs like crack or cocaine; the fact that it leads to amotivational syndrome which basically leads to a life without much success). If this does not work then enlist a trusted family member that's maybe closer to his age that he respects or admires to speak to him about the dangers of drugs. Finally enlist the help of a school counselor. Maybe there are community resources available to help. Good luck.
Alanon works. Paradoxically, nagging and giving all the reasons for losing interest in pot are likely to fail. Two suggestions: 1. Go to some alanon meetings and learn what effectively helps one deal with family and friends who are abusing substances. 2. Provide positive alternatives. Rather than say no say yes to all the healthy alternatives there are.