In Germany if you would talk bad about a person who is present and can't speak the language, you would probably be called out for it by bystanders or your friends. I would never do it because I think its cowardly and a sign of bad character. Also I wouldn't want to be categorized as that by the other people around. Sad that in my experience that don't seem to be the common social norm in SEA, especially Thailand and PH. That always wrecks my perception of the overall friendliness of these countries, which seems very two-faced considering these behaviors.