What is the oldest written source in this country that mentions this right?
Indonesia
The Indonesian right of association is first asserted in their 1945 Constitution, ratified on August 18. The right was asserted in Chapter XA, Article 28E (“The 1945 constitution of the Republic of Indonesia”, 1945).
1945. The 1945 Constitution of the Republic of Indonesia. August 18. https://jdih.bapeten.go.id/unggah/dokumen/peraturan/116-full.pdf.