He said the incident took place when tensions were already high in the country following the death of his close ally Johana Ng'eno in a helicopter crash in Nandi County.
Kamillan told reporters that he was beaten using a chair and that his leg was targeted during the alleged assault.
He said he had been missing for several days which raised concern among his supporters and the public.
Many people had earlier claimed that he was abducted and held in unknown conditions before he reappeared and spoke out.
In his statement Kamillan thanked God for keeping him alive and said he was now recovering and in stable condition.
He urged those involved in abductions or illegal acts to stop and respect the constitution of Kenya. He also praised Raila Odinga saying the opposition leader had helped protect the country from abuse of power and unlawful killings.
Kamillan said he plans to seek medical advice and also work with health leaders including Anyang Nyong'o to improve cancer care in Kenya.
The claims have sparked strong debate online with many people reacting differently to the allegations and the activist return. Some have called for a full investigation to uncover the truth while others question the details of his account.
The events come amid growing political tension in the country where calls for accountability and justice are increasing each day.
Authorities have said they are looking into both the alleged assault and the earlier disappearance to establish what really happened during the period.
Leaders from different political sides have also reacted to the claims calling for calm and respect for the law as investigations continue.
The activist remains vocal about his experience and insists that justice must be served to protect citizens from similar incidents in the future.
He also said he will continue to speak out despite pressure from unknown forces and will stand firm on issues affecting the public and his community.
The story has drawn national attention and is expected to remain a major topic in the coming days as more details emerge from ongoing inquiries and official responses from relevant institutions. Many Kenyans are watching closely as the situation develops and await clear answers.