I will bet no street Vendors anywhere will ever pay tax - nobody keeps records they will divulge to the Tax office. Any customer ever got a receipt for anything?? Same goes for most businesses in the markets - very little accountability - and not just in Bangkok!
The only accounting going on is counting the takings!
The Tax department need some sort of accounts to show outgoings and income!
Street food can be encouraged with proper management by the Authorities to ensure quality hygiene practices, enforced by regular inspections. Will corruption hamper theses ideals? Sorry to say, I think so!
I think many street vendors make a pile and have got away with little overheads that restaurants have for example!
About time time they were reined in and started paying their dues.
By the way, I like Street food!