The two teams meet at the Sher-e-Bangla Stadium in a re-match of the finals of the tournament held in Sri Lanka in 2012, reports CMC.
West Indies have had to stage recovery missions in the middle overs after top order batting collapses on their way to the round of four.
"Our top order has to come good and give us that start within the first six overs, so that the other hitters can come in and play their natural game," said Ramdin.
"The win against Pakistan was great. We got a confidence booster and we are happy at the moment."
Sri Lanka and West Indies have won three matches and lost one each in the group stages.
Both teams have been outstanding during the power-play overs, taking wickets and restricting the runs.
"Sri Lanka is a tough team to beat but once we continue to play smart cricket, I seen no reason why we cannot get into the finals," said Ramdin who created a T20 record of four stumpings against Pakistan.
"They are very tricky, they have experience with guys like Mahela Jayawardene, Kumar Sangakkara and Tillekeratne Dilshan and so we need to walk with our A-game when we meet."
Man-of-the-match in the game against Pakistan, Dwayne Bravo has listed team unity and support for Captain Darren Sammy among factors responsible for West Indies success in the tournament.
"We have no malice in our team, whether it is Sammy or Gayle as the captain we support them and this is why this team is doing so well," said Bravo, who was named-man-of-the-match for his 26-ball 46, after West Indies plundered Pakistan Tuesday.
"We are looking forward to the semifinals and we know that Sri Lanka are used to the conditions, they just won the Asia Cup here and they will be dangerous".