It is definitely a species of Hemidactylus gecko – the claws originate from the top mddle of the expanded toe pads. To me it looks more like the Four Clawed Gecko (H. mutilatus) than the Asian House Gecko (H. frenatus). This can be confirmed if the inner digit on the feet lacks a claw. The patterning of lighter coloured spots, without similar sized darker flecks or streaks, is more typical of H. mutilatus. Both species are common occupants of houses in Bali.
The animal should definitely NOT be released. It does need to be euthanized for two reasons. Firstly, it may carry a disease (virus, bacterium or parasite) not present in Australian lizards or other reptiles (or even other animals). Secondly, it may be a female with stored sperm, and therefore have the capacity to produce offspring and establish a new population here.
There are two main options that I would suggest. You can phone Biosecurity in SA and have them come and collect it. Alternatively, you can dispose of it yourself. The humane way to do this is to cool it down it down in trhe fridge for say 20 minutes, just so it is very slow moving. Then crush the entire head with one swift blow from a broad hammer or brick, so that death is instantaneous.
Do whatever you find easier, just do not let it loose.