Acknowledgements 1 The dynamics of bilateral trade balance: The role of exchange rate, income and cash balance (An e mpirical case for ASEAN countries) 1.1 Introduction 1.2 Some principal facts around ASEAN trade 'cheap' labors are specifically dominant to be employed among middle firms. Besides, the reason of less competitive in the international market also should be taken into account. Although still showing positive signs, the coefficients of productivity lose their statistical significance when the models are applied for large-sized firms. However, in general, our findings corroborate the self-selection hypothesis.