Five tones instead of six, no glottal catch anywhere, v said as y, d and gi said as y, and final n and t drifting back to ng and c. It is softer and more sung than Hanoi's, and it is what most overseas Vietnamese speak. Two limits of working from the site's Hanoi transcription rather than from the spelling: the reference has already merged r into /z/, so the rule that sends /z/ to /j/ catches r-words too, which Saigon actually says with a retroflex or a trill; and Saigon keeps s (retroflex) apart from x, which a rule on a single /s/ cannot show.
Where: Ho Chi Minh City and the Mekong delta
The way in: Say 'Việt Nam' as 'Yiệc Nam', with the ệ low and dipping rather than cut off.
Try a word
Anything the spelling engine can transcribe, the accent can move. Slow it down to hear the shape.
A wider, more musical pitch range, with the merged hỏi-ngã tone swooping down and up. A little slower, and the final stops less abrupt.
What moves, one rule at a time
In the order the mouth applies them. Every before-and-after is playable — click the IPA. The pattern is the rule as the engine runs it, for the curious.
Consonants
v is said as y
v → j
How: Do not let the teeth touch the lip; start from the y of 'yes'.
The south never developed a /v/; the letter v is read as the glide /j/. vui 'happy' sounds like 'yui', Việt like 'Yiệt'.
Word
Reference
Accent
vui
happy
Việt Nam
d and gi are said as y
z → j
How: The y of 'yes' again.
What Hanoi says as /z/ for d and gi, the south says as /j/: dạ 'yes' is 'yạ', gì 'what' is 'yì'. The reference has folded r into the same /z/, so r-words come out with /j/ here too; Saigon really says those with a retroflex /ʐ/ or a trill.
Word
Reference
Accent
dạ
yes (polite)
gì
what
final n drifts to ng
(?<=[aăɤɤ̆ɔou])n(?=[˥˦˧˨˩ˀ]|$| ) → ŋ
When: after a back or central vowel, at the end of the syllable
How: Let the back of the tongue close instead of the tip.
ăn 'eat' comes out 'ăng', bốn 'four' as 'bống'. After the front vowels (i, ê, e) the n stays.
Word
Reference
Accent
ăn
to eat
bốn
four
tin
unchanged — front vowel
final t drifts to c
(?<=[aăɤɤ̆ɔou])t(?=[˥˦˧˨˩ˀ]|$| ) → k
When: after a back or central vowel, at the end of the syllable
How: Close at the back of the mouth, unreleased.
The same shift as n → ng, on the stops: mất 'lose' as 'mấc', một 'one' as 'mộc'.
Word
Reference
Accent
mất
to lose
một
one
Melody
hỏi and ngã become one tone
˧˥ˀ|˧˩˧ → ˨˩˦
How: Drop, then rise — with no catch in the throat.
South of Huế the broken-rising ngã and the dipping hỏi fell together into a single low dipping-rising tone. The spelling keeps both marks; southern children learn which words take ã as a list.
Word
Reference
Accent
mã
horse; code
mả
tomb — now identical to mã
hỏi
to ask
nặng loses its glottal catch
˨˩ˀ → ˨˩˨
How: Go low and let the syllable finish on its own.
Southern nặng is low and slightly dipping, and the vowel runs its full length; the Hanoi cut-off is gone.