Do I have to include thesis topic/advisor name after career change?
You are not obliged to include any information in your CV, IMHO, neither morally nor legally.

Of course, people can be asking what were you doing if you got your masters (let's say) in 2012 and started your current PhD programme in 2015, and they'll likely ask you in an interview about this. Or (especially if there are no interviews, which is the case for many PostDoc programmes) simply not consider your application because of the "grey areas".

As for whether to do this or that: Remember that in academia, CVs are very verbose and usually contain all relevant information. If you're deep into your current PhD and you have some publications, I don't think that listing details on your masters is necessary. I, for one, do not list the names of the supervisors at all; they are obvious from my publication record.