Many of these markets are squatters on public property and encroach on private properety owned by merchants trying to make a living for their family.

Give them an inch and they take a mile. Same with vehicle rental offices, push cart venders, etc they have no onsite parking so they take public parking which property owningt /renting, merchants depend on for potential customers to come into their bonified business.

The question is why have these property owners allowed them to use their space for so long.

For the money.

.......Google Rot Fai Market Ratchada

That is where the action is.........

Yes I have been there and very little like Klong Thom and all the junk , more like JJ market at night, where did the small guys selling junk go ?