How to check Kernel Version and install topic

Hi all,

Could you please advise me about How to check Kernel version and install Kernel ? I've facing on battery fast draining without any running application. 40% losses while my phone is idle status in 6 hours. I've fix with flash a new firmware but the problem still living (it normal around a week then happen again).

I need official kernel (Country = THL)

PS. if I flash a new Firmware that's mean including Kernel ? as I understand Kernel is a path in Firmware


Thank you all !!!