There is another route... costly one.
RP Dip in Biomedical Science --> Monash University's Bachelor in Biomedical Science --> NUS Medicine.
RP linked up with Monash for the accelerated bachelor programme. :) So if cost and age is not an issue.. you can consider this route. Quite a handful of RP Biomed students are heading towards the Monash bachelor programme.
nus medicine takes about 250 ppl /yr
NUS dentistry about 50/yr.
By right, the requirements to enter these medical courses are Math, and any 2 of the 3 sciences, physic, chem, and/or bio.
but usually, they wouldn't take the non-bio students, since the taking of biology is an indication of interest in the subject.
with over 2000+ applicants for the limited places, they can afford to be extremely picky.
and TS, i suggest you do well for your subjects first. 50s and 60s ain't exactly grades which can get you into the med/dentistry courses.
these courses require straight As in your A levels. and A lvls is much harder than O lvl.