LSM-15 pair with LTM-5

For a 3 way switch, that is only on/off (no dimmer needed) I need LSM-15 and (2) LTM-5… will this work?

Yes. One or more LTM-5 remotes can be used to control the LSM-15.

Just to be pedantic, (1)LSM-15 and (2)LTM-5 would be a 4-way switch combination.