Indochina-a peninsula of southeastern Asia that includes Myanmar and Cambodia and Laos and Malaysia and Thailand and Vietnam. Indochinese peninsula. Southeast Asia-a geographical division of Asia that includes Indochina plus Indonesia and the Philippines and Singapore.Burma, Myanmar, Union of Burma-a mountainous republic in southeastern Asia on the Bay of Bengal; much opium is grown in Myanmar.ndochina. n. 1. (Placename) Also called: Farther India a peninsula in SE Asia, between India and China: consists of Myanmar, Thailand, Laos, Cambodia, Vietnam, and Malaysia.