Elon Musk has hit back at the man who oversaw the successful rescue of a Thai soccer team from a flooded cave after he rejected the billionaire's offer of a miniature submarine as "not practical for the mission".

Musk tweeted that "former provincial governor" Narongsak Osottanakorn had been wrongly described as the "rescue chief", adding that Osottanakorn - the man who rejected his sub - is no expert in cave rescue.

The former Thai provincial governor (described inaccurately as “rescue chief”) is not the subject matter expert. That would be Dick Stanton, who co-led the dive rescue team. This is our direct correspondence: pic.twitter.com/dmC9l3jiZR

— Elon Musk (@elonmusk) July 10, 2018

The actual expert, according to Musk, is a man by the name of Richard Stanton who encouraged him to build the submarine, saying it "may well be used", according to the Daily Mail.

READ MORE: Comment: It's time for Elon Musk to pull his head in

Elon Musk designed a child-sized submarine out of rocket parts that he hoped could be used to rescue some of the soccer players trapped in a flooded cave in Thailand.

Musk tweeted a conversation between himself and Stanton in which Stanton encourages him to keep working.

According to Musk's transcript, Stanton told him that dive teams are "worried about the smallest lad' before encouraging him to "keep working on the capsule".

Musk assures Stanton that he will, adding that his team are designing the capsule so the occupant can survive even with two failures occur, just as he does with his spacecraft.

But he adds: "I don't want to put it on a plane if you think important changes are needed."

Stanton responds: "It is absolutely worth continuing with the development of this system in as timely a manner as feasible. If the rain holds out it may well be used."

Elon answers: "Right now, I have one [of] the world's best engineering teams who normally design spacesuits working on this 24 hours a day.

"We are trying to get it right in a very short period of time.

"If it isn't needed or won't help, that would be great to know. Otherwise, it would be very helpful to have as much design direction as possible."

While Mr Osottanakorn ultimately decided Musk's craft wasn't needed he appeared to thank him for his efforts, describing the technology as "good and sophisticated".

Musk had earlier put out an optimistic tweet saying he was "leaving [the submarine] here in case it may be useful in the future."

He was also shown inside the cave where rescue efforts are being staged and held a meeting with rescue teams before departing.

Testing underwater in LA pool pic.twitter.com/CDO2mtjP2D

— Elon Musk (@elonmusk) July 8, 2018

All 12 players and their coach have now been rescued from the cave after spending more than two weeks trapped underground.

It was initially thought that the team could have to spend up to four months inside the cave until floodwaters receded.

But further rains forecast for this week spurred rescuers into action, amid fears the water level could rise again and drown them.

Musk tweeted Tuesday morning he'd "Just returned from Cave 3," referring to the rescuers' command center inside the sprawling cave.

Just returned from Cave 3. Mini-sub is ready if needed. It is made of rocket parts & named Wild Boar after kids’ soccer team. Leaving here in case it may be useful in the future. Thailand is so beautiful. pic.twitter.com/EHNh8ydaTT

— Elon Musk (@elonmusk) July 9, 2018

He posted photos of the cave interior and a video showing members of the rescue team working their way through chest-high water.

Earlier this week, Musk posted videos of the sub being tested in a swimming pool in California with simulated narrow passages like the cave.

Cave Three is about two kilometers (1.2 miles) from the entrance of the cave network and is the base for Thai rescuers.

The footballers still awaiting rescue are about two kilometers further in, at a point very difficult to access.

By Monday night, elite divers had managed to bring out eight members of the football team which included 12 boys and their 25-year-old coach.

The Thai rescue effort has been assisted by experts from around the world, and the death of a former Thai Navy SEAL diver who ran out of oxygen in the cave on Friday underscored the dangers of the mission.

After garnering headlines with initial ideas of installing a giant air tube inside the cave complex and using his firm's penetrating radar to dig holes to reach the boys, Musk offered his idea for the mini-sub.

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.

Last week, Musk said he was sending teams to Thailand from his private space exploration firm, SpaceX, and engineering firm, Boring Co. which is developing tunneling systems for transport projects.

While offering the mini-submarine as a potential savior, Musk used the opportunity to promote space exploration. He is also co-founder of the Tesla electric car company.

The Thai soccer team ventured into the Tham Luang cave complex after practice and became trapped by rising waters more than a fortnight ago.