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Your transfer time is ok. Kuala Lumpur is an easy airport for transit. When you land at the airport, do not go to the immigration area, simply look on the monitors or ask airline employees to help you and find the gate for your flight to Bali and go to that gate. You do not have to check in again if both flights are on Malaysian Airlines.

Because you do not have to go through immigration, you likely do not need a Malaysian visa. But to be sure, you should let us know what country your passport is from and research that more yourself too.