Should I work in Vietnam or continue studying abroad?

I came here with a visa for both tourism and work purposes. However, the visa only allows me to be employed as a manual laborer, and I can only work for an employer for six months. If I want to work here longer, I'll have to find a different employer at least twice a year.

I've been here for seven months. Back in Vietnam, I worked in information technology. My salary was considered decent compared to the national average. Before I came to Australia, I thought about experiencing life in the country by applying for part-time jobs to make up for the money I plan to spend obtaining my doctorate degree. Before moving abroad, I had a lot of ambitions. I thought living in a new country would help me grow as a person, make new friends and gain valuable knowledge. I was extremely excited just thinking about it.

But after having been here for a while, things are not as I thought they would be. Life here is very bleak. The houses and shops don't feel welcoming and convenient as they are in Vietnam. I have no friends, no means of transportation, and I'm working as a manual laborer. The job pays well but I'm burdened by heavy negative thoughts. I can't seem to get used to the food here and I've lost 3.5 kgs. I've been living here for quite some time already, but I have yet to feel a part of the Australian environment. Now I wonder if I should return to Vietnam or apply for another Australian student visa to complete a PhD in information technology. I'm considering two options:

Option 1: I stay here to study for two years. My tuition fees would be nearly VND900 million (US$38,200). I can only afford the first year with the money I've earned and saved so far. I plan to work and study at the same time for the first year to save for the second year's tuition. I asked some friends here for advice and everyone said that option would be difficult. They told me that working part-time while studying would barely cover my living costs, and that would be no way for me to also afford tuition fees. If I focus too much on working, I’ll neglect my studies. If I try to pursue a PhD wholeheartedly, my family can’t afford to provide any financial support, so everything will be up to me.

Option 2: I go back to Vietnam. I continue to apply for jobs in the IT sector like before. Everything will be back to the way it was before I came to Australia. Life will be easier, I won’t have to worry too much. I’ll have friends, family and a job. But I’ve been thinking about this for so long now. I’ve been given the opportunity to be here in Australia, and if I go back, who knows when I’ll be able to return here again? Besides, I’m not that young anymore, it will be too late to either work or study if I delay my decision any further.

I’m still single, with no family obligations or children. I know my life is up to me, but I’m questioning the future so much. I look forward to your advice.