There are a few things I’ve learned about scams in Vietnam in my time here that I wanted to share. So here they are in no particular order.
Taxis. They are unregulated, which means they can charge whatever they want. And if you’re a foreigner in an airport or train station, you’re seen as an easy target. Best way to avoid scams is to only use a company you can trust. Vinasun and Mai Linh are the two I recommend. If you arrive at the airport in HCM, walk to the taxi stand (outside the terminal, straight ahead). Ignore everyone who asks you if you want a taxi until you find the stand with Vinasun or Mai Linh on it. They will get you a metered taxi. Do not get into a taxi without a meter — they will charge any amount they want and there’s nothing you can do about it. In town, the same rule applies when you’re trying to flag down a taxi: only use Vinasun or Mail Linh (there may be other reputable companies but this is based on my experience and the recommendations of friends here). Also, it’s a good idea to keep a lot of small bills with you. It makes your wallet fat, but you’d be amazed how often taxi drivers “don’t have” change for your large bill. On the other hand, it’s good to round off to nearest 1000 VND or so. In other words, don’t make the driver, who makes barely enough money to support his family, go digging around in his pocket for 5 US cents.
Drinking. Saigon is not a place where you can let your guard down and drink as much as you want. If you’re a drunk foreigner, especially walking alone, you may as well have a bullseye on your back. You’re leaving yourself wide open for pickpockets and other scam artists. Also, if you’re drinking in a bar and the tab comes at the end of the night and you’re drunk, you’re pretty much going to pay whatever the bar charges you. As a foreigner, and after a night of drinking, you have no credibility with the police.
Restaurants. Most are mainly honest. But I’ve been overcharged before and it’s easy to be fooled. You don’t know the currency well. You get a bill and you just pay it. This is probably more likely to happen at restaurants that cater to foreigners. I once had a single beer and a plate of sausages and was charged almost 500,000 VND (about 25 USD), an outrageous amount of money here. It wasn’t until after I left that I put it together and by then it was too late. Always examine the bill carefully and if you have a question, ask before you pay.
Don’t let all this scare you. Vietnam is mostly very safe and people are friendly and accommodating. But in the big cities especially, you can’t let your guard down.