After putting 169 runs on the board, the Indian bowlers managed to bundle out the home team for just 27 runs as none of the Malaysian batswomen touched double digits.
Opting to bat first, the women in blue began the proceedings on a shaky note, losing opener Smriti Mandhana (2) and Vastrakar (16) for just 35 runs in 6.1 overs.
However, Mithali kept one end safe and forged a crucial 86-run partnership for the third wicket with skipper Harmanpreet Kaur (35 off 23 balls) to take her side past the 100-run mark.
Harmanpreet fell in the 15th over with India's scorecard reading 121 runs. later, Deepti Sharma chipped in with an unbeaten 18 runs to help India reach 169 runs.
Mithali's 97-run knock came off 69 balls, which contained 13 fours and a six.
In reply, Malaysia were off to a disastrous start as they host lost half of their side within the first five overs with the score at just 12.
Captain Winifred Duraisingam (5), Sasha Azmi (9), and Zumika Azmi (4) tried their best to put up some resistance. However the entire side succumbed before an experienced Indian bowling attack in 13.4 overs.
For India, Vastrakar was the wrecker-in-chief with figures of 3/6 from three overs while Poonam Yadav and Anuja Patil bagged a couple of wickets each.
India will now face Thailand in its next tie.
Brief Scores: India women 169 for 3 (Mithali Raj 97*, Harmanpreet Kaur 32; Ainna Hamizah Hashim 1/30) beat Malaysia women 27 all out (Sasha Azmi 9, WA Duraisingam 5; POoja Vastrakar 3/6,) by 142 runs