Each new READ operator starts to read data from a new line. That is a reason why your code does not work properly, as you expected.

If the @lastchance's solution READ (33,*) A will work - it is OK. If not, the straightforward way will be just to make a cycle until end-of-file or until nx*ny numbers is read. At each cycle iteration you would read six (or less) numbers and put them in the corresponding matrix entries.