if you use the new SDK from the SAP HANA Cloud Platform you no longer have a changing password. Once you open the tunnel you'll get an initial password for your HANA instance in the cloud. After changing it to your needs you can always use that database password to connect your HANA Studio to the HANA instance on your account.
But be aware that you have always 2 passwords. The one you use to create the tunnel and the other one that you use in your HANA Studio to connect to your HANA instance in the cloud.
Get the new SDK at https://tools.hana.ondemand.com/#cloud
Hope this helps.
Best, Rui
PS: We'll be repeating the free online course "Introduction to SAP HANA Cloud Platform" (https://open.sap.com/course/hanacloud1) around April/May this year. In week 2 and 3 of that course you'll also learn how the "new" tunnel works.