What are best career options for someone interested in drawing and painting and currently in 12th standard with science and maths?

Your passion for drawing/painting and exposure to math/science will benefit you in two areas: design and animation.
In both cases, you’d be collaborating with technical departments to put your ideas or thoughts into action. As a result, having a scientific and math background would be advantageous.
Product, fashion, graphics, industrial, and accessory design are only a few of the numerous sub-areas of design.

Careers in design -
There are artistic directors and technical directors in animation. The concept, characters, and plot are all created by creative directors. The thoughts are brought to reality by technical directors. This, too, need coordination with the technical department.