On Vietnam's political history website, there are often "maps of Vietnam" that draw Laos, Cambodia and Vietnam together, and there is even a situation where the two Cantons of Our country are drawn together, so why does Vietnam do this?
Personally, I think it is necessary to start from three aspects:
Ancient factors
The ancient history of Vietnam and the ancient history of China can be described as closely related. In Vietnamese history, the South Vietnamese regime at the end of the Qin and the beginning of the Han Dynasty was regarded as the "Zhao Dynasty" of Vietnam, so in the Vietnamese concept, Liangguang belonged to them as a land "since ancient times" - this year was known to the Qing rulers of China as early as the Qing Dynasty. Therefore, the Vietnamese monarch of the Nguyen Dynasty sent an envoy to Beijing to request the Qing Dynasty's Jiaqing Tianzi to crown him "King of South Vietnam", in a vain attempt to lay the groundwork for the future plot of Liangguang. However, this trick of the Vietnamese was already recognized by the Jiaqing Emperor, so the Jiaqing Emperor crowned the Nguyen Dynasty monarch as the "King of Vietnam" - since then, Vietnam has had its current name.
In ancient times, Vietnam copied China both politically and culturally, and among them, it also imitated China's tributary system, and in Southeast Asia, it became the boss behind closed doors, coercing ancient Laos, Cambodia, and Champa (in present-day southern Vietnam) to pay tribute to Vietnam.
In the ancient concept of Huaxia Tianzi, the tributary regime was part of its own rule. This concept was accepted by the Vietnamese, so in the ancient historical map of Vietnam, the Vietnamese would draw Laos, Cambodia and other countries that had tributary relations with Vietnam in the ancient Map of Vietnam.
Recent factors
In modern times, the whole of Asia, with the exception of Japan, has either been colonized or semi-colonized. In this case, Southeast Asia is not immune.
In the Indochina Peninsula, except for Siam, the rest of the countries were divided up by the British and French colonists, of which Burma was annexed by the British and later included in British India; while Vietnam, Laos, Cambodia and other countries fell into the hands of France.
Just as the British integrated India and Burma and centralized management, the French, in order to improve management efficiency, also merged Vietnam, Laos, and Cambodia, established the French Indochina colonial regime, and established the center of rule in Hanoi.
After World War II, the original colonialist system collapsed. Vietnam was initially divided into north and south parts. With the completion of the unification of Vietnam, led by North Vietnam, the Vietnamese authorities began to be ambitious again, considering the establishment of a Vietnamese-led Indochina federation within the scope of French Indochina – and Vietnam did have actions – such as infiltration into Laos and armed invasion of Cambodia.
Contemporary factors
In contemporary times, with Vietnam's comprehensive national strength ranking among the best in the Indochina Peninsula, many Vietnamese angry youth began to swell up, with the bad problem of map opening up. Many of the absurd maps on the Vietnamese Web come from this. However, this is also a manifestation of the expansionist ideology of Vietnamese society.