The two men came from behind as Worachet Pakeerut parked his car. One punched him in the face and the pair sped off on a motorbike.
"It happened so fast I couldn't see their faces," the law professor and activist said of the attack, which left him bleeding and needing hospital treatment. "Fortunately, other people could see them and were able to describe them to the police."
Days afterwards, the men - brothers - turned themselves in. They told police they attacked the professor because of his campaign to change a strict law relating to the Thai monarchy.
The attack on Worachet underscores the increasingly bitter nature of a struggle over Thailand's controversial "lese majeste" law, which outlaws criticism of the royal family, in a battle that threatens to reopen old political wounds.
Campaigners such as Worachet say the law is unfair, unaccountable and has increasingly been used against political targets and to quieten dissidents. But groups who want to retain it, and have taken to the streets to demonstrate, say it is important for retaining harmony with the country. They say only those who intended to insult the monarchy are charged.
