is it true that the city of Bankok has exerted all floating houses
from the city, during the last decade(s)?
you have to mention a trustworthy source. 
try to say something about the boundaries of the area in which
floating houses are no longer allowed.
additional information on the situation in bankok with regard to
floating houses may be tipped.

Excluded all floating houses from the city?
That could be a a matter of definition  - what is the city.  This
travel bureau site still advertises that houseboats can be seen in the
klongs, but maybe those are not within the "city".

http://www.unisonthailand.com/bangkokhalfday.htm

For decades, the klongs within the city have been reduced (as were the
waterways in Hamburg a hundered or more years ago), so, no doubt,
there are less houseboat dwellers than there once were.
Myoarin