As far as the double employment is concerned, until and unless you complete the required formalities from the present employer it will be treated as double employment. If the present employer knows about where abouts of yours there is every possibility of sending a copy to them also about your status and even if they may go with a publication of your details in the news paper also which may affect your career.
Thanks and regards - kamesh
Second, do not think over absconding, this is not an ethical step and by doing this you’ll not be able to provide any previous employment /experience/relieving certificate to any future employer bcz the current employer is not gonna give you exit clearance as you are expecting NOC or company Y is asking for you to obtain. Also you just have started your career life, you shud not do anything like ABSCONDING
This is not a dual employment but an absconding case which can bother you in future in manyways..
I would suggest you, if you have recently joined this present company and looking for company Y just bcz of good option with salary, need to complete your training first bcz you can get many more good options in future.
“Stay here and complete your training first”