It's an Asian thing. The Chinese are super loud. Also the Vietnamese, who can sound like they're having a blazing row when they're just having a chat. At least the Thais have a relatively pleasant sounding language.
In many circumstances, Thais can be a lot quieter than foreigners. But when it comes to "noise pollution" type noise (cars, motorbikes, music), the Thais are trying pretty hard to be the best at it.