I dea s to harmonize the regulation of ‘corporate shares’ (CS) in the corporate law of Indonesia and Singapore discussed in order to start up and embody the ASEAN Single Market. T his article focus ed on different minimum standards and requirements (MS&R) in the transaction CS within two different corporate laws of Indonesia and Singapore. It is necessary to employ a conceptual approach, especially corporate share as a very basic of a company, to have a comparative legal analysis to reach a solution. Further more , it is to harmonize such standars and requirements on the CS transaction . I t is necessary to use the theory of negative regional economic integration that significantly different with the conservative theory aplied inthe EU. As a result, the different regulation of CS between those two different company law regimes should be simplified by withdrawing their similiarities of MS&R. This may cre ate an avenue to achieve the ASEAN’s single market in 2015. This new standar (model) would ease the process harmonization in which companies of ASEAN Countries can make a cross-ownership of CS by the mergers and acquisitions of transactions that timely make a strong position in the business competition regionally. I conclude that harmonization of MS&R of CS provided in company laws of Indonesia and Singapore would become a cornerstone for the ASEAN Single Market in which obstacle of joint market has been minimized or even abolished. However, harmonization of MS&R of CS should be in the corridor of sustainable global justice in the ASEAN market competition.Therefore, I recommend that both Indonesia and Singapore should develop a corporate culture in the spirit of the ASEAN Single Market, and review t he regulation regarding company law of both countries, especially the CS and legal procedures of the cross-bo r der mergers transaction and acquisition.