I speak Cantonese, Vietnamese, and Mandarin. I also did research in this matter and I will share with you some facts.
Cantonese is considered an older dialect in Chinese branch, and Vietnamese have many Chinese loanwords, aka ‘Han Nom’. Those Chinese loanwords are somewhat pronounced exactly the same as Cantonese.
Eg: 人 is ‘nhân’ (in Vietnamese), which is pronounced /ɲən / in both Vietnamese and old Chinese, while Cantonese pronunciation is /yan/. The ɲ (= Spanish ñ) used to exist in older Chinese dialects.
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To add more to the examples of similar pronunciation between Cantonese and Vietnamese:
- In Vietnamese, ‘chúc phúc’ or ‘祝福’ in Cantonese are pronounced exactly the same. It means to wish someone luck.
- ‘斩’, or ‘trảm’, which means to behead someone, are pronounced exactly the same.
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Many Chinese linguists study Vietnamese, Korean, Japanese to decipher Old Chinese phonology.
There are even speculations that Vietnamese spoke Cantonese in the Middle Age, since the early Vietnam Kings are Chinese decendants. Vietnam are close to Guangdong, Guangxi, so they share many similarities in terms of language.
Straight to the main question:
+Vietnamese has 6 tones:
- The first one is a bar (called ‘thanh ngang’ in Vietnamese). It’s just a simple ‘ahh’ sound in English, this sounds exactly the same with the third tone in Cantonese.
- The second tone is ‘à’, which sounds exactly the same with the fourth tone in Cantonese.
- The third tone is ‘á’, which sounds like the first tone in Cantonese.
- The fourth tone is ‘ả’, which sounds like the second tone in Cantonese.
- The fifth tone is ‘ã’, which is a little bit like the fourth tone but the Southern Vietnamese never pronounce this tone. So you can say that it is native to the Northerners.
- The sixth tone is ‘ạ’, which sounds exactly like the fifth tone in Cantonese.
All the Vietnamese tones, except for the tidal wave ã, are similar to the tones in Cantonese.
There is this special consonant ‘ng’ as in 我, which exists in Cantonese and Vietnamese too. But many recent Cantonese speakers cannot pronounce this consonant any more due to the evolution of Cantonese.