@Rio *********
It's what I would do. If you arrive visa exempt there is nothing to do ahead of time except filling out your TDAC.
The odds of immigration asking to see proof of onward travel are very low. It's more likely the airline would ask for that before letting you check-in. But they can ask for that on a tourist visa as well, since both visa exempt and tourist visa are both tourist entries. (Though to be fair, the odds are lower if you have a tourist visa).