Gunmen shot at the anti-government protest stage in Khao Saming district, Trat province, at 9.30pm on Saturday.
Some 2,000 people were listening to Pong Sarakham on the People's Democratic Reform Committee (PDRC) stage in Yingcharoen market when gunmen on two pickup trucks drove by, Suvichan Suwannakana, a PDRC spokesman in the eastern province said on Sunday.
The men in the first truck threw grenades at a noodle shop nearby where 20 people including PDRC guards were sitting.
Those on the other truck fired indiscriminately at the noodle shop and then turned their guns to the stage.
According to the latest unconfirmed report as of 11am on Sunday, one was dead, a five-year-old child, and dozens wounded.
Khao Saming is 300km to the east of Bangkok.
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