May I assume that you read https://lkml.org/ ? If you research the contributors, then you will be able to identify where they work and thus identify any possible job openings.

Google's Fuschia project might also be of interest.

In general, kernel level programming requires years of experience. Most of the work entails device drivers and sub-systems, e.g. filesystems, networking -- all of which rely on knowing standards and their implementations.

Being located in SE Asia, I would think that equipment manufacturers could be interested in your skills in writing device drivers for their products. Another area might be embedded systems, which in addition to Linux might use one of the BSD variants.

In order to be effective at the low-levels, you need a good grasp of CPU architectures and their many idiosyncrasies. In addition to x86-64, ARM and RISC-V knowledge should be very applicable.