Is it possible to train a toddler to keep the toys automatically after they have played with it ? Any tips ?

Yes it is :) Set by example, and make it fun too! In fact, the younger you start, the more likely they'd follow through. Firstly, be sure that your child is done playing with the toy - if your child takes it out again or makes a mess with it, that means he/she is not done playing! Once you know that your child is tired of the toy, you can start with a cleanup song - you can make up your own, or there are songs that you can reference to on YouTube and sing it to your child. Keep them with your child and encourage him/her to do so too, you can also make it fun by turning it into a game :)

Mine went to playgroup so she learn from there bcoz her peers are doing it. I tink basically is not do it for them and show them how to keep? Pick up a toy with their hands and guide them back to keep i guess?

Yes it is very possible! Must be determined and persistent in training them to keep. Initially keep the toys with them, Slowly you slow down your pace and let your toddler to keep it all

yes. I train my boy from 18 months onwards. keeping it fun and doing it together, praising him when he does it, after a while it becomes a habit.

Yes by being role models ourselves. My 2 year is "trained" to keep his toys at home and in child care.