I got an invitation from Chinese work company mentioned single entry visa. I want to make some provisions for coming back to India during holidays. Thus, I want to apply for double entry or multiple entries. What is the best possible way to get that?
The best possible way to get it is to ask your employer for a new letter stating that you will be making multiple visits for whatever reason -- normally the wording is something like "we intend to have <name> visit multiple times between <date> and <date a year minus a day later> for <reasons>". Then apply for a multiple entry visa as normal.
China, generally, don't give out multiple entry visas to first time visitors without good reason. If you haven't been to China before then the company there may have deliberately asked for a single entry knowing that you would be unlikely to get a multiple entry. You should talk to the company, particularly, if you've been to China before, explain the situation and your holiday plans (have some concrete reasons for wanting to come back, not just generic 'holidays') and ask then if there's anything they can do. It's possible, even likely, they'll suggest coming over on the single entry and getting another visa for the next time. After a few trips it should be easier to get a multiple entry visa if required.
Failing that you can just apply for a multiple entry visa anyway, attaching some details saying that although the company is requesting a single entry visa you'd like to be able to come back for some specific reasons. The problem is that it's possible your entire application may be denied -- although it's more likely they just choose to issue a single entry if they think you're eligible (or maybe a double entry if you're lucky).
It's difficult to say more without knowing more specifics, which is why you should talk to the company. If they've done this before they should probably be able to advise you. Alternatively you can look for a local visa expert where you are and talk to them, they may have some other ideas (although be prepared to pay for that service).