BANGKOK Three Thai soldiers were killed and five wounded in a brief clash with intruding ethnic Karen guerrillas near the border with Myanmar on Tuesday, military officials said. They said about 50 armed fighters of the Democratic Karen Buddhist Army (DKBA), a Myanmar-based guerrilla group operating along the border, had entered western Tak Province and launched a predawn attack on Thai troops and villagers in the area. About 20 houses were also damaged in the clash, Reuters said.