"She had been tied up and forced to undergo cruel training known as crushing to prepare her to work in the tourist industry.
"We freed her and helped her to recover. She became really close to me and we formed a strong bond.
"I went in the river to show just how remarkable the relationship with humans is. And that if you show warmth and kindness to them, they will treat you well, too."
Kham Lha tries to lift Darrick up by her trunk.
Crushing is a brutal training method where young elephants are tied up and beaten into submission.
The method is used in Thailand's elephant tourism industry to make elephants more subdued and safer for holidaymakers to ride.
After being rescued, Kham Lha now wanders freely through the protected jungle sanctuary with dozens of other elephants.
A spokesman at the Elephant Nature Park said: "We're all really pleased with Kham Lha's progress and how well she's adapted.
"She's now a happy young elephant. The video shows just how close she is to Darrick and it's an important lesson to be kind to animals."