Final answer:
Portugal, The Netherlands, and France were the three European countries that conquered Indonesia, Malaysia, and Indochina. The Netherlands became the dominant power in Indonesia while France established control over Indochina. Britain's presence was also significant in Malaysia.
Step-by-step explanation:
The three European countries that conquered parts of Southeast Asia were Portugal, The Netherlands (Dutch), and France. Portugal took control of Malacca in Malaysia in 1511, but their presence in the region faced resistance due to their efforts to convert people to Christianity. Subsequently, the Dutch became the dominant European power in Indonesia, with no interest in spreading Roman Catholicism.
The region known as Indonesia was once referred to as the Dutch East Indies. In Indochina, which includes present-day Vietnam, Laos, and Cambodia, France established its colonial claim, known historically as French Indochina.
The British also played a significant role in Southeast Asia, particularly in Malaysia where the regions of the Federation of Malaya, Singapore, Sarawak, North Borneo, and Brunei used Malaya and British Borneo Dollar as currency. Each of these European powers left a significant impact on the culture, economy, and political structures of the regions they colonized.