His funeral will be held at Wat Bang Toei from April 16-20, the foundation announced on social media.
Nathee, who served as the foundation’s secretary-general, recently suffered a stroke and had been in a coma following surgery.
He and several other volunteers launched Issarachon, which means “free people”, in 1996, initially organising activities for homeless children and later expanding to assist other underprivileged groups, such as slum dwellers.
The group was incorporated as a foundation in 2005 and its volunteers continue to provide counselling, medications, condoms, snacks, drinking water and books to people in need.
The foundation publicises their plight so that state agencies and the general public can better understand their needs and offer assistance accordingly.