Photos of ex-Thai Navy Seal diver Saman Kunan, who died during the mission, ex-Chiang Rai governor Narongsak Osatanakorn, who died on Wednesday, and Wild Boars football team member Duangphet Promthep, who died earlier this year in England, were set up in the area to commemorate their passing.
The ceremony was presided over by Mae Sai district chief Narongpol Kid-arn and included the offering of alms to 39 monks and a religious ceremony to pay respects to sacred things in the cave and pray for the prosperity of all those who were involved in the brave rescue mission.
The members of the Wild Boars football team, as well as their relatives, were present at the ceremony.
In June 2018, the world was transfixed for 17 days as an elaborate international mission unfolded to rescue 13 members of the Wild Boars football team after they were trapped by rising water in the Chiang Rai cave system.
The 200-metre-deep Chamber 1, which visitors use to enter the complex, was the command centre for a rescue operation led by Narongsak and the Thai Navy Seals.
Saman, also known as 'Sergeant Sam', lost his life on July 6, 2018, as he was trying to rescue Wild Boars football team members.
Wild Boars team member Duangphet died on February 12 after collapsing at a football academy in England. Narongsak, who was dubbed "Wild Boars Governor" for his able leadership during the crisis, died at Siriraj Hospital in Bangkok on Wednesday (June 21) from colon cancer.