Rejected by the Immigration

and I wanted to ask you , you think because they black list me im not able anymore to do some transit on this country ???

One thing to learn from this: As a foreigner trying to enter a country, you have no rights and that country's authorities can deny you for any reason they like - it does not matter if wrong or false, you cannot do anything!
Of course drugs is a very sensitive issue in Singapore (as you probably knew). The test turned out positive and you confirmed their suspicion (then claiming that weed is not a narcotic didn't help either).

Every ICA webpage has a "Contact us" link at the upper right corner, which leads to a page giving you all addresses and phone numbers.
If you need to contact them by email, just enter "email enquiries" into the search box on top of the page and you get a list of email addresses.
This is so simple and obvious that I really wonder how you could have spent four hours without finding it. Maybe your brain suffered from your past drugs use?

It is possible to change flights at Changi Airport without clearing immigration (and thus despite a ban), but they can (and sometimes do) check for drugs and others in the transit area as well.

Sorry to hear your story. It’s something shouldn’t have happened but you should aware of Singapore law, which is toughest against drug users.
I should suggest avoid visit here as they will have all your data, includes the incident happened with you, may create trouble in future, if you visit again.

Coming back to your request, I had shared ICA contact email link many times in previous threads. Here you go again:

https://www.ica.gov.sg/technical

If ICA officer confirms that you can travel in future, bring that email confirmation but it doesn’t give you guarantee a walk over at immigration checkpoint. The officer still can deny your entry to Singapore. Good luck

thanks for you reply , my last question is im not able to do transit on this airport anymore ? I mean if I buy a flight to go somewhere else and I need to transit at Changi airport they won't let me take my next flight because of whats happen??? I mean you tell to not visit Singapore on this point I'm totally agree with you and honestly I don't want to go there for visit but just for flight connection it will be the same problem ??

Fusella wrote:

thanks for you reply , my last question is im not able to do transit on this airport anymore ? I mean if I buy a flight to go somewhere and I need to transit at Changi airport   because of whats happen they won't let me take my other plane ?

Chances are less that they will track such cases through transit via Changi airport but you won’t surprise if they do, as their system can track anyone and everyone who has landed Singapore using AI. Try to avoid, if possible.

alright so even if I don't need to cross the immigration they can stop me on the transit and send me back where I come from. so I have to avoid the connection in Singapour everytime now ... thats really weird because in Asia so many flight are connected with Singapore so I need to solve the problem with them just to be able to do transit

I had already answered your question about transiting at Changi Airport.
Yes, you should definitely try to clear the matter with ICA if you intend to travel in Asia again!

Could you pls just tell me which service I need to contact ?

Fusella wrote:

Could you pls just tell me which service I need to contact ?

Their help desk email for entry visa. Request them to advise if you can enter again.