vivo Malaysia has uploaded a teaser for vivo S1 which shares similar design with vivo V15. Still, there are some difference between the vivo S1 & the V15.
The vivo S1 offers a multi pattern visual highlight on the rear panel while the design outlook appears similar with the vivo V15. There is also a triple rear camera but lack of the rear fingerprint sensor on the vivo V15.
More details to come soon!