From what I understand the Singapore clinic sends you across the border to Malaysia to do the actual PGD (gender selection of embryos). Although it's not a long trip.
The only concern here is that the doctor from the Malaysian clinic thinks their government may ban gender selection in the next coming year or so. But they haven't yet so we can still hope.
The Malaysian clinic is very respectable. They have been a fertility and womens health clinic for at least 10 years. So if the law doesn't change it's a great option.
I'm not sure of the name of the Singapore clinic which collaborates with the Malaysian clinic but I know the Malaysian clinic is called TMC Fertility.
Gender selection in Singapore is not allowed.