Introduction

The incentive for me to write these short stories began from a comment I saw on YouTube.

"ThaiViet doesn't make sense; Thailand and Vietnam never interacted in history. A/Vietnam or Thailand/B is better since they did have connection through history."

According to what I've seen, this sentence has been said by at least three fans from three different ships. So I decided to write several short stories - some on the shared history between Thailand and Vietnam, some on random ideas that I had in my head (2P!ThaiViet, 2P!Southeast Asia, for instance).

For the introduction, I will simply say a few things.

1. Considering formal diplomatic relations (***their interactions apart from the wars***), Vietnam (Dai Viet) and Thailand (Siam) already had a good relationship during King Gia Long and King Minh Mạng's reigns in the beginning of the nineteenth century. King Gia Long helped Siamese troops in their battles against the Burmese, and Siam also protected him, helped him ascend to the throne in his country and establish the Nguyen Dynasty. Therefore, King Gia Long, just moments before his death, had told his court that his nation must retain good relations with Siam (1).

Therefore, afterwards, when Myanmar asked Vietnam to form an alliance to beat Thailand in 1824, she downright refused since she did not want to upset Thailand (2). When his King passed away, her King dismissed the court for 3 days to express his grievances (3).

(1) (2) Woodside, Alexander. Vietnam and the Chinese Model: A Comparative Study of Vietnamese and Chinese Government in the First Half of the Nineteenth Century. Boston: Harvard University Asia Center, 1988.
(3) Dương Duy Bằng. "Quan hệ giữa Việt Nam - Campuchia - Xiêm giai đoạn 1802-1834". Southeast Asian Studies. 4/2006. p18-26

2. On the "connection" meaning the wars between Thailand and Vietnam, I'll give you a brief list to search online.

1. Dai Viet-Lan Xang war (1478-1480): It doesn't have a Wikipedia article in English, but its existence has been proven by the paper The Ming factor and the Emergence of the Viet in the 15th century and the book series Chronicle of Ming (which detailed on historical events occurring in China and its neighbors during the Ming Dynasty). And they both mentioned the involvement of Lan Na and Ayutthaya.
2. Siamese-Vietnamese war (1718).
3. Siamese-Vietnamese war (1771-1772).
4. Siamese-Vietnamese war (1833-1834).
5. Siamese-Vietnamese war (1841-1845).
6. Dai Viet-Siam War (1785).
7. Vietnamese border raids in Thailand.

There were in reality at least 13 wars in total. The relationship between Thailand and Vietnam in history cannot be summarized in a few simple pages. A scholar could write a book about it.

If you love a pairing other than ThaiViet, it's fine. However, please think reasonably and do proper research.

Endnote: Check out Hetalia ThaiViet・東南コンビ【Golden Lotus】on Facebook if you're interested.