By JANET MASLIN Published: April 12, 1984 ''TURUMBA,'' the second feature by the Philippine film maker Kidlat Tahimik, unfolds in a gradual and deceptively deadpan style. It takes place in a small village, where the festival of the title is an occasion for every family to make papier- mache figurines. Beginning by showing the various customs that surround the festival, it follows the process by which one family starts a manufacturing operation, eventually producing 25,000 toy dachshunds for the 1972 Munich Olympics. ''Turumba,'' which opened yesterday at the Film Forum, is acted in a slightly stiff style, since it is just scripted enough to lack spontaneity. That does not mean it is without wit, however. Mr. Tahimik's screenplay interjects all sorts of incongruously Western locutions, like ''export order,'' into the speech of the villagers, and has them marvel over each new dividend that their prosperity brings - a radio that pl...