Lalrindika Ralte and Jeje Lalpekhlua scored from the penalties in the 36th and 86th minutes while Alwyn George and Romeo Fernandes also found the net in the 68th and 76th minutes at the Sultan Qaboos Stadium here.
Italmazov Farhad pulled one back for Turkmenistan in the 59th minute.
India are now on seven points from four matches in Group A and next play hosts Oman on July 3.
Turkmenistan played to a defensive plan in the opening half and India had to wait till the 36th minute to break the deadlock.
Romeo Fernandes, India's super-sub against United Arab Emirates, made justice of coach Arthur Papas fielding him in the starting XI. As he broke through with a sudden burst inside the penalty box, rival defender Komekov Hemayat found it best to bring him down.
Midfielder Lalrindika Ralte stepped up cooly to take the resultant penalty and slotted the ball past Turkmenistan goalkeeper Garayev.
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Barely four minutes after Ralte's penalty conversion, Alwyn George got past two Turkmenistan defenders but his prompt left-footer hit the post.
After the breather, Turkmenistan started off with more purpose and the first five minutes saw the Indians defending. Indian captain and goalkeeper Gurpreet Singh Sandhu had to stretch back to palm away a deflection. MORE