The groups are demanding Thak-sin Shinawatra resign unconditionally as acting prime minister and let someone accountable spearhead political reform. They also called on the opposition to boycott the snap election scheduled for April 2.

Soontree Hatthee Sengking, of the Network of Khon Kaen People for Democracy, condemned Thaksin's decision to dissolve the House.

She called it Thaksin's second act of tyranny. The snap election was an attempt to protect his personal interests and it gave his Thai Rak Thai Party an edge over other parties, she added.

Thaikorn Pholsuwan, a leader of Thai Isaan for Democracy, said the Network of Khon Kaen People for Democracy would head south from a site on Mitraphap Road.

Demonstrators from other provinces were using different routes to avoid police checkpoints out of fear that officers might try to block them, Thaikorn said.

More than 3,000 protestors were waiting at Lam Takong dam in Nakhon Ratchasima for the others to arrive, said Prakit Roopsoong, another leader of Thai Isaan for Democracy.