Behind the unmarked door of a shoplot along a quiet commercial stretch of Forest City in Malaysia’s Johor state, four customers sat tapping away, playing slot-style games on tablets. A stern-looking man stood guard at the entrance, his eyes darting around. The customers could place bets starting from around 20 ringgit (US$4.89). Instead of handing over cash, they paid for gambling credits using Malaysia’s Touch ’n Go e-wallet. They were then issued tablets from behind the counter with...