Is it ok for me to train my 4-m.o. on how to stand-up or is it too early for that?

No. Do let your child develop at his own pace. There are milestones at each month for children to meet, and standing is usually a milestone for 11 month olds. Is your baby able to sit up unassisted? If not, why are you trying to make him stand? Standing comes after crawling. You could hold him up in a standing position but he should always be supported. http://www.babycentre.co.uk/x1048872/when-will-my-baby-stand http://sg.theasianparent.com/baby-at-12-months-milestone-checklist-for-proper-baby-development/