我想知 do 可唔可以放係verb 前面

Indeed, it is an answer form when asked: John, do you play tennis?
John answered: I do play tennis or -Yes, I do play tennis.
So, I do play tennis is absolutely correct & formal.
Following samples are same with do before a verb:
Do you smoke? Ans: Yes, I do smoke
Do you eat a lot for dinner? Ans: Yes, I do eat........

如果將do放係一個verb面前，一般都係加強語氣。
例如：I do love you. 即我真的很愛你。
而你的example: I do play tennis.
就係我真係識得打網球。
一般都是口語用法。

唔可以. 要寫成: I play tennis.
你有冇見過 "You do play tennis?"
冇呀麻. 好似中文咁,講出來:肥肥白白 寫出來: 白白胖胖
明5明? 5明可以mail 我[email protected]

yes u could use like this, but only in informal english, like i DO love somebody....i DO like somethings, it used to emphasize the "verb", in your case, i DO play tennis, means u can play tennis very well.......

correct me if i'm wrong!!