The Prospective Marriage visa (subclass 300) is a visa which you have to apply for from outside of Australia. The purpose of this visa is to take your Thai fiancée from Thailand to get married in Australia. Note that like most fiancée visas there is a time limit. The visa is only valid for 9 months once you enter Australia. You need to get married in Australia within this 9 month period.
If this is a same sex marriage then you need to speak to an immigration lawyer about your options such as the Australian partner visa. As gay marriage or same sex marriage is not recognised in Thailand or in Australia and t has its own requirements for Australia. See the Australian Partner visa for more details on this website as this visa is based on marriage however you can apply for this visa based on a de facto relationship and not based on marriage.
This has become a common Australian visa in Thailand as more Thai nationals settle in Australia and start a new life. This visa allows the parents of a Thai national now living in Australia (if their child is an Australian citizen or permanent resident) and is settled in Australia to apply for the visa and live with their children.
If you are a Muslim in Australia and wish to take your Thai wife back to Australia then you can apply for an Australian Spouse visa or if you are not married an Australian Fiancée Visa. If you are planning on getting married in Thailand as a Muslim then there is another process to follow before you register your marriage in Thailand.
The temporary Australian skills visa for a Thai is available under certain circumstances. If you wish to work in Australia then you would need to comply with the rules and regulations of the temporary skills visa for Australia. The conditions for this Australian visa has been listed below.
If you are not able to apply for an Australian Skills visa and you fit the requirements for the Australian working Holiday visa then you can work temporarily in Australia on this visa. Note the requirements of the visa and also the length of stay allowed in Australia. If you are married to an Australian national then you would be best suited to apply for an Australian spouse visa or fiancée visa. These are listed on this website.
Note that there are two types of Australian work visas. This is a subclass 417 visa which a Thai national cannot apply for. As a Thai you can only apply for the Australian Work and Holiday Visa (subclass 462). This visa is limited to certain nationalities which are listed below. If you wish to holiday and work in Australia then see the other visa which a Thai national can apply for in Thailand.