INDOCHINA, Southeast Asia Mainland🇲🇲🇹🇭🇱🇦🇰🇭🇻🇳 Mainland Southeast Asia (historically known as Indochina and the Indochinese Peninsula) is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to the west and the Pacific Ocean to the east. It includes the countries of Cambodia, Laos, Myanmar, Singapore, Thailand and Vietnam as well as Peninsular Malaysia. The term Indochina (originally Indo-China)