The Family Act of Australia determines the outcome of any financial arrangements made before marriage. In the West this financial arrangements are normally called a prenuptial agreement. You can also after marriage arrange for a post-nuptial agreement however court intervention would be needed for this as it should not be of any detriment to your creditors in Australia or in Thailand. This would become a very expensive process to complete.
See the note made on prenuptial agreements if you are getting married in Thailand and planning on taking your Thai wife back to Australia. If you are staying on in Thailand then the property laws would be as listed below. Marital property in Thailand is divided into personal property and community of property. The definitions are much wider than it would be under Australian law. Take legal advice on all property matters before you get married.