I finished my phd on 2017 , nearly a year and half. Since then, i have not had chance to do any project research for some circumstances. As my job asked me to apply for poster or presentation in a conference, due to career obligation, i have thought to do poster from my phd thesis, my question is that possible to do ?
Yes, you can. Colin Purrington has some extremely good advice on how to go about it. There are even templates you can use.
Edit: You've added that your thesis was published in a university library. That's OK. It is your work, so you are allowed to present it in a different form. Your poster is going to summarize the problem you tackled and showcase the relevant results. You shouldn't try to present the entire thesis as a poster; only the very most important parts..