Groups urged Thai authorities to investigate attacks on pro-democracy activists Sirawith Seritiwat after he was beaten and left unconscious on a sidewalk in the latest violent incident

Amnesty International submitted open letters to Thailand's defence minister and its police commissioner asking them to bring to justice attackers who have targeted three vocal pro-democracy activists on multiple occasions since the military seized power in a coup in 2014.

The ruling junta actively cracked down on dissent and political discussions while it enacted new election laws that favoured its leader, Prime Minister Prayuth Chan-ocha, in elections in March.

The appeal follows the latest attack last Friday on Sirawith Seritiwat, who opposes the military's role in politics. He was beaten until he was unconscious on a sidewalk near his home in Bangkok in broad daylight.