My pay is at 1.8k/month which I do not expect to increase in the near future. And I have plans to study uni part time next year and it is quite near to my workplace. Should I stay or resign?

I assumed that you are still in a very young age. If that is the case, you should probably quit your current job and study full time instead. Studying full time gives you a chance to mix around with different people and it may help you in the future.

What I learnt about at a career course it sometimes Job A will get you to a Job B but ultimately a Job C.

So take it as stepping stones if you would like to move on.

Another consideration is if they allow you to work flexibly while you study part time?

If you are looking to change career track or working environment, how about lifeguarding?

Everywhere in Singapore shortage of lifeguards. Full time or Part Time or Freelance - all are welcome.

Some are office hours. Some are rotating shifts. Some you pick the timing you available to work.

You need Lifesaving 1 ➡️ Lifesaving 2 ➡️ Lifesaving 3 ➡️ Bronze Medallion

Reach out to me or anyone in the lifeguarding community.

What you are going through at work is common. Ultimately, it boils down to the culture of the company that will trickle down to how the employees behave and how the company hires. Of course, it's not 100%.

Based on what you have mentioned, I would advice to talk to your seniors at work or your superior about your intentions of getting a part-time degree.
If they are receptive to it, stay on until you complete your degree. If not, move on to a new job to encourages growth and learning.