You can use the supplied power supply 12V/12W or use the screw terminals. The screw terminals support 12-24V DC.
Thinka version HKV 1.3 and up can be powered with the KNX bus. Thinka HKV 1.2 and before requires 12 Watt, so the KNX bus power is not sufficient as it provides around 320mA over 30V (less than 10 W) and it needs to power more than just your Thinka.
See also Thinka versions.