Rescue chief Narongsak Osottanakorn described Elon Musk's technology as "good and sophisticated" but unpractical for the evacuation operation.
Elon Musk flew to Chiang Rai on Monday night to donate a child-sized submarine in the hopes it would be used for the rescue.
"Leaving here in case it may be useful in the future. Thailand is so beautiful,” he said in a message posted on Twitter.
'Small enough to get through narrow gaps'
He called it "basically a tiny, kid-size submarine using the liquid oxygen transfer tube of [a] Falcon rocket as hull."
Musk said it was light enough to be carried by two divers, robust, and small enough to get through narrow gaps.
The person inside need not swim or know how to use oxygen bottles.
He posted video of divers escorting the pod during testing in a Los Angeles swimming pool
With the evacuation two-thirds complete, Narongsak said he did not see a role for the mini-sub.
“The equipment he gave us is not practical for our mission,” Narongsak told reporters.
“His equipment is technologically complex and advanced, but we cannot bring it into the cave for this mission.”
Musk's visit to cave site welcomed
General Anupong Paochinda said Musk had a 30 minute conversation with Thai Prime Minister Prayut Chan-o-cha at the Chiang Rai Mae Fah Luang Airport before he travelled to the cave.
Anuphong said the pair spoke about rescuing the remaining five people inside the cave.
He said Prime Minister Prayuth also urged Musk to invest in the country’s Eastern Economic Corridor.
Musk left the submarine at the cave site, and also gave advice to a group of local surveyors.
The group thanked the entrepreneur for his "guidance".
“Thank you Elon for providing us lots of useful equipments and guidances from your engineering team," the group of surveyors wrote on Facebook.
"It’s an honor for our Thai Geographer team lead who joined the meeting last night. We wish you have a beautiful time in Thailand,” read the post written in English."
Elon Musk's idea has attracted praise and criticism from social media users.
Users @Saigonbear and @Junkojang offered their profound gratitude, thanking him for making "plans about rescuing the kids quietly".
Others crticised Musk's contribution, calling it a "PR stunt".
- with AFP.
