JAKARTA, April 11 (Reuters) - Southeast Asian stocks traded mixed on Monday as global uncertainties lingered, while the Indonesian index extended losses ahead of the release of economic data later in the week. Malaysia's stock index lost 0.3 percent, while Thailand's SET Index gained 0.2 percent, extending gains from Friday. "Oil price rebound should reinforce investor confidence on risky assets. However, uncertainties are expected to linger ahead of the OPEC/non-OPEC meeting scheduled o