Near Carpark A, drive into Labrador Villa Road.
Weekends can take bus 408 to bus stop id 14419, weekdays have to walk a fair bit from Pasir Panjang Road.
eh...not sure If I got it correctly..
The last time I went, I followed the pdf http://www.nparks.gov.sg/cms/docs/diy_guide/Labrador_guide.pdf from Carpark C to Carpark A then to Carpark B (went 1 round..)
So, the general direction is walking more towards CP A?