Guys, i have solved the prob already.
Well long story short.. the root cause was the.....
STANDARD ALARM !!!!
1st, some friend of mine (friend's friend) who is a myvi addict claimed it was the alarm and say old Persona has this issue n standard. I did not believe as he said forums mostly are fake. (he said not me) . I did show him the video and he said it must be alarm if immobilizer sure sounds like dead battery. (i tried bcoz i have a key with no immobilizer, it was right)
then a senior officemate told me, his savvy having the same issue with the alarm after removing it was ok.
So i removed the standard alarm, which was behind the car.
Now already months. My car starts normal and easily even when it sounds it will die (just like the alarm issue), it can still start the car.
p/s offtopic: where to remove immobilizer??