There is no tax for ICO. But because you say that Singapore and Japan impose an ICO tax. yes that might happen, because there are some countries that have submitted tax applications.
"ICO tax" is there such a thing? Even if there is no tax called "ICO tax" their developers need to pay other kinds of taxes. Mainly because they have earned something from the selling of their ICO. Nothing is left untouched by the taxes system as if there is one they will always find a legal loophole with the system that is why taxes are so vague that it covers all kinds of ways on how a individual or entity is earning money. Just imagine how the world will be if they see a legal way on being exempted with tax if that happens no one will be paying their taxes.