can i conquer same battlefield multiple time in one turn for the sake of card trigger ?

No, you cannot.

According to the RiftJudge FAQ (ID 2676, 7023, 2805, 1500) and Rule 465, you can only score each battlefield once per turn, regardless of whether you score it by holding it (at the beginning of your turn) or by conquering it (during the main phase).

Because conquering is defined as gaining control of a battlefield you have not yet scored this turn, the following restrictions apply:

1. Once per turn: You cannot conquer a battlefield if you have already scored it this turn (either by holding it or a previous conquest).
2. Triggers: "When you conquer" triggered abilities only trigger if you successfully score a point by conquering. If you have already scored that battlefield earlier in the turn, a subsequent change in control does not count as "conquering," and therefore those triggered abilities will not trigger.

In short, even if you move units in and out of a battlefield multiple times, you can only trigger "when you conquer" effects for that battlefield a maximum of once per turn.