Singao is mother fucker in cuban spanish. Also if you just want to take the spanish word for fucker and mother and put them together it would be Madre (mother) Chingado (fucker male) or Chingada (fucker female). I prefer the cuban version since it is just quicker.
Coma mi panocha singao! or Chupa mi pito madre chigado! That is mother fucker in spanish, the cuban version and the smart ass version.