I have seen many mini-trucks blasting (> 90 dB) psy/techno music while driving around Yangon with some decent sound system. Example:
Why are there some mini-trucks blasting psy/techno music while driving around Yangon?
I have seen many mini-trucks blasting (> 90 dB) psy/techno music while driving around Yangon with some decent sound system. Example:
Why are there some mini-trucks blasting psy/techno music while driving around Yangon?
Seems to be a sort of celebration:
The road from jetty to the city was clogged with people in a celebratory mood. Loud speakers–giant black boxes decked on mini-trucks–blared loud and shrieking music on a road filled with revelers dancing wildly. Source
However there are extremely few sources online or even none that give any answers as to what, so this is the best I can give. Even though the author saw this in Mandalay, it seems to happen throughout Myanmar, especially since the description exactly matches yours.