Kwanchai Praipana was shot twice and taken to hospital after gunmen in a pick-up truck sprayed bursts of gunfire at his home in Udon Thani, according to another leader of the group, Jutaporn Promphan.
The government introduced the state of emergency yesterday in the wake of a string of attacks that have mostly been aimed at demonstrators protesting peacefully in Bangkok.
Grenade assaults on Friday and Sunday killed one man and wounded more than 60 people alone, bringing the casualty toll since November to at least nine dead and more than 550 hurt.
The emergency decree allows authorities to ban public gatherings, impose curfews and censor local news reports for 60 days.
But the government said it would not use those powers to crack down on demonstrators who have seized several patches of the capital, so life in the city continued as normal, with tourist sites unaffected and no major deployment of extra security forces.
Army commander General Prayuth Chan-ocha said "we will have to see" whether the decree helps ease the violence. He urged both sides to talk, saying: "We must stop this conflict to let the country move forward."