The problem with primary care is that it is volume based work. Primary care doesnt pay for expertise. It pays per consult. Yes you can charge more for extra time spent. But it doesnt work out to your advantage. It is better to see more patients per hour. The other thing with primary care is that it is breadth of knowledge. So much to know and discuss with patients. And because there is so much breadth it is hard to form a team to assist you.

Whereas with specialists you can be much more efficient.

Not only are people more willing to pay higher rates for specialist medical consults but you can also have a team od specialized educators or para clinical staff helping. So dr can do the medical assessment. Determine diagnosis is correct(usually referred and differentiated problem for you ) assess that there are no contraindications to the treatment you offer then explain briefly to the patient then pass them on to another junior dr or nurse educator etc.
Very *ahem* specialized.

With GPs usually you got to do most of the work. Diagnose. Investigatr from scratch. Explain differentials. Then results then what possible treatments answer objections and fears. It is A LOT of work. And from derm problem to gynae problem to pediatric to orthopedic to psychatrict to neurologic to cardiac to urologic etc how to build a support system? Even in OPS got some nurses is for DM HPT Obesity Smoking cessation at most only. Which is why..refer. but who eill pay you big bucks for referring?

So despite all the rhetoric and adulations about GPs dont fall for it. It is still more lucrative to spcialize. Look for niche markets that are not filled by existing specialties.

That is how aesthetics started. Other fringe medicine opportunities are out there one could specialize in. Singapore unfortunately doesnt have rural centres where there migjt be demand for specialist GPs in anaesthesia or obstetrics or surgical assist.