Capacitor and resistor in parallel in output 19V laptop charger
I cannot figure out why it leak ac while also providing DC 19V

It likely leaks low levels of AC current in both DC output leads because the noise reduction circuit inside the charger has a Y capacitor from DC output to the live or neutral AC wires, This cuts down high frequency noise from the internal high=speed flyback transformer but, a side effect is that it leaks low level 50/60 Hz current to the output DC wires.

I want to reduce the current or make it safe to work

It's not normally regarded as a problem and is safe but, you may have a faulty charger and maybe you should consider replacing it. If you can measure the AC current with a DVM, it should be around 1 mA to earth.

Also giving capacitor of 25V and resistor in parallel does the job.
But will it cause any problem in future ?

I think you are connecting them from the DC output to earth and if that works then it's likely that your charger isn't &quot;dangerous&quot; or faulty. However, check with a DVM on the AC range measuring current and see what you get - if it's around a milli amp then it's safe. If it's above 5 mA then there might be a problem: -

Table from here.