Razer Pin Cards can be purchased at convenience stores like 7-11 and Cheers. In order, to top-up Gems using these cards, head down to the PapayaPlay Cash Shop, select BlackShot SEA.

Then, click the Razer Gold Pin Top-Up button at the Cash Shop page (bottom of page). Enter the serial number and pin number (you gotta scratch off the card to see it) in the screen that follows to top up. Simple!