By Theerawat Thongma,
The ugly scene took place on Tuesday evening.
The couple said that the volunteer didn't see the boy sitting between the couple on their motorcycle when he accosted them for making a U-turn upon seeing the checkpoint on Soi Khao Talo.
He struck the toddler on the head, knocking him unconscious and opening a 10-centimetre wound that took three stitches to close.
The boy repeatedly vomited afterwards, indicating a concussion, and was found to have bleeding on the brain.
His mother, 25-year-old Kalaya Tomklang, said she would file a complaint with police.
“We were just avoiding the checkpoint so we wouldn’t have to pay a fine,” she said in tears. “Is that so serious a crime that you have to overreact like that? Now I’m just worried about my son’s health. He’s my only child. I want justice for him.”
The incident went public when a person who met the couple at Bang Lamung Hospital posted the details on Facebook.