The OP has declared that he is not George Soros and his assets in Oz are VERY simple.

A simple Will drawn up here can be done fr less tham 3,000 Baht. I doubt that cost is an issue for the OP but he certainly does need to return to Australia for such a simple task.

What is FAR more important is that the wrng question is being asked. The Will is a product of the OP wishes in the event of his demise. The first job is to establish what those wishes are and then fit the Will to those wishes.

There is not enough details to be specific but,

Do you want to be cremated or buried ?

Here or Oz ?

If here, do any Oz family want ashes etc?

Are you married ?

If married you have a legal obligation to make adequate provision for your spouse.

Who do you want to benefit from your estate ?

Do you actually have assets in Thailand - at best, bank accounts, car, motorcy, perhaps condo.

A Will covering assets in Thailand and a Will covering assets in Oz (cross-referencing each other) is the sensible way to go.

The Wills should only be produced when you are 100% clear on your wishes.

Sorry, I'm not qualified to give advices on investments in Thailand or Australia. Talk to specialists (but I do not trust people for hire) or to older, more experienced friends, if any.

As to the other questions, - once I'm dead I do not care whether I'm buried, cremated, eaten or preserved here or any other place. How I die is another matter, even more important than when...