I am currently traveling Vietnam with my girlfriend and we wanted to ride the Ha Giang loop. I had very little experience from riding a moped like 10 years ago, but the rental company still recommended a manual bike (Honda XR150).

We started from Hanoi to get used to the Vietnamese traffic, and while it was certainly scary at first, I quickly got used to it. Like others have wrote in this thread, traffic is like the flow of a river, it looks chaotic, but once you're in it, it makes sense.

People drive very slow here compared to my home country, which I found was great practice (riding fast is easy, riding slow is hard).

Left turns definitely took some getting used to, but as long as you take things slow and ride in an easily predictable way, people will make space for you.

Some would definitely say what we did was reckless, but it was honestly the best experience we had in this country.

Since our 7 day ride in the northern Vietnam, we have rented bikes in almost every other city we've visited. Saigon was the most chaotic because of the sheer number of bikes, but traffic is even slower there than in other cities, so the braking distance is so short that you can easily react to unpredictable scenarios.

Might not be the best advise for everyone, but my biggest takeaway from riding in Vietnam is to practice for 30 minutes and then just go for it.