do you tip in hanoi, Is tipping culture prevalent in Hanoi, Vietnam?

Tipping Etiquette in Hanoi: Is It Customary to Tip?

Immediately after taking off from Hanoi Noi Bai International Airport bound for Singapore today, the customs officer scrawled the word "Tip" on my ticket. He took my passport but never returned it to me. I asked him what he intended to do, and he kept pointing to what he had written. I didn't know what to do, nor to keep trying to get help from anyone, my flight at that time was just minutes from departure. Eventually, I caved in, and I had to pay 500,000 VND. I have since reported this incident to the Ministry of Foreign Affairs of Singapore, and while I realise it might be normal in some other markets, I did feel helpless, being forced to bribe him to get my passport stamped.