You can call nirvana and see what they have to offer? Idk as a secular person ayam don't give a shit how my body is handled after death, it's none of my business anymore, ideally I would like to have all my organs donated where feasible or maybe donate body to science (but I can't find options for this in Malaysia) and then just be cremated and thrown wherever but I guess it's up to next of kin, as a non religious person I don't care which religious rites they choose. Does your father himself care, that it has to be a non religious funeral for him?

Can consider something like this:

https://www.facebook.com/naturalburialmalaysia/

Burning is a waste of resources really.

Its not really a grave, the body and coffin gets absorbed back into the land and become nutrients for nature. So you're not wasting land, you're giving back to it.