If you are from Thailand (or from any other country) and you want to visit Australia you will have to submit an application for a visa. All foreign nationals are required to have a visa to enter Australia, even for a short visit. Citizens from Thailand are considered to be ‘high risk’ which means that there is a concern that if a visa is granted the holder of the visa might want to stay on in Australia longer than is allowed or may breach one or more of the other conditions attached to their visa. It is up to the ‘applicant’ for the visa to persuade the Australian Government that they do not present such a risk. As a Thai citizen you will have to fill in and submit an application form as well as other documents to support your application.
Your supporting documentation will usually include identity documents as well as financial documents which show that you have funds available to support your visit to Australia. If you have a bank account you might want to show your bankbook; if you have a job you might want to show evidence of that such as a letter from your work or a pay slip. If you own land or a house you might want to show evidence of that. Each application is different and you need to structure your application to show the Australian Embassy that you are a person of means and are low risk.
If you have an Australian friend or boyfriend he may be able to assist you application. By writing a letter of invitation he can not only make an offer to invite you but he may also be able to show that he can support your visit in some way. If he works or has funds available he can offer to financially support your visit. He can attach documents to your application such as a bank statement or a pay slip. How much money you or he might want to show depends on the length of your proposed stay and what activities you will be doing, etc.
Your boyfriend does not have to write a letter of invitation for your visit – you may be able to apply for an Australian Tourist visa all on your own. As mentioned above, it will depend on your personal circumstances. Because applying for a Tourist visa is so complicated we do advise citizens of the Thailand to speak with a visa expert – it can make the difference between success and failure.