Is it good to have a drink which contains soy protein, hi-maize, vitamin (a c b6 b12), thiamin b1, niacin b3, folate, (folic acid) sodium, potassium in pregnancy ?

Not clear: You should certainly discuss it with your obstetrician if you become pregnant. If you are placed on a vitamin by your doctor while pregnant, you should consider stopping this supplement though. (Not sure if this is a routine in Australia, but it is in the United States) Regardless, your doctor's advice should be most important here. Good luck.

Which form: Which forms the vitamins are can matter. For example, B6 comes inactive and also active. The active form of B6 is pyridoxal-5-phosphate. Too much inactive B6 can actually block active B6 from the B6 receptor, creating symptoms of B6 deficiency. Folic acid is synthetic, and too much can be bad also. Methylfolate and folinic acid are what one should take during pregnancy.