They walked along streams, refilling used plastic bottles with dingy drinking water and setting up tents in abandoned poacher camps, sometimes just hours after their targets had left. Many of them spread black tile grout on their faces for camouflage.

They ate rice and beans, sometimes with some fried crickets or silkworms as added protein.

One of the men on patrol, who goes by the name of Maung, was a former rosewood poacher now turned ranger. After being arrested and imprisoned for six months, he said he wanted to apply his knowledge of poaching tactics to make things better in the forest instead of continuing the problem.

He also runs a volunteer group that takes children into the woods to teach them about the trees.

“From now on, I’ll never give up this work,” Maung said. “Will do it until I die. I want to teach the next generation to learn to love the forest. Then they’ll know not to destroy it.”

Ben C. Solomon reported from Ta Phraya National Park, Thailand, and Richard C. Paddock from Bangkok.