I will start by providing some little context: I was interning as a developer at a company A while I was in last year of my college, one year back. Since it was still a pandemic in my country, the company was reluctant in rolling a full-time offer. It wasn't the best company in terms of work culture, I had only sticked there for such a long duration because my team had very talented people with whom I was enjoying a lot working with. In the end, I ended up joining another company B for my first full time offer as SDE.
So right now, 8 months later, my former manager from company A has contacted me that they have got fresh round of fundings and all and they are trying to correct the work environment and all and wants me back for a new project. The company seems to be ready to offer me the role of SDE-2. (Few discussions are left but my former manager has said it will be mostly formalities)
Of course I am attracted by the idea of a promotion but I am concerned about few things. I am currently very content at my current company but I do feel from time to time that I am a little underpaid. So I thought to have a discussion with my current Manager regarding the offer I have received and would like him to consider increasing my offer(don't want them to match but at least increase the offer so I don't feel like I missed a good opportunity).
Should I have this conversation because I don't want to harm my current relations at the company. I cannot ask for a promotion since they have different levels as compared to other companies and require at least 2 years for promotion.
I want help on how to start and guide the conversation with my manager to have a fruitful discussion. Would be happy to provide any other points. Advice on any other aspect is also very welcome!
Thanks in advance!