The court found Arnon, 40, guilty of defaming the monarch after charges were brought by public prosecutors. The lese-majeste law carries a maximum jail sentence of 15 years, reports the Bangkok Post.
Arnon served as co-leader of a youth-led democracy movement that staged protests in Bangkok in 2020 that drew hundreds of thousands of people demanding the removal of then-prime minister Prayut Chan-o-cha, who had seized power in a coup.
Prosecutors told the court that Arnon posted three messages on his Facebook account on Jan 1, 2021 in a way that distorted information with the intent to insult the royal institution.
The court said the evidence provided by prosecutors was reliable and that it found Arnon’s testimony, where he insisted he wrote the messages in good faith with the aim of seeking amendments to Section 112, unconvincing.
Arnon had previously been sentenced to four years and fined B20,000 in a separate lese-majeste case involving a rally in 2020.