I don't think it had anything to do with an argument, it was obstructing the driver who beeped at him. This can be typical of some Thai drivers who become incensed at the sound of a horn and have their fragile egos bruised.
Posh Medica also sold at 7/11's. I found 1/2 the packet was more than enough for a major cleanout, in fact a couple of tablespoons would probably do the trick.