How to extend the power and volume buttons on a tablet (Linx 7)?
The button board is two pieces, one the conductive carbon or metal button, and two the pcb with some open traces. When the buttons are pressed, they flex and touch two sides of the traces on the pcb. If you peel it apart, you get access to the traces that you can solder to easily. 

That said, you can use a wired headphone cable with volume and play remote buttons, or even a bluetooth remote instead. Or if your tablet supports USB OTG,  a wired keyboard.