There may be times when you need to think about asking the copyright holder for permission to use their work in your thesis.
If you use more than a reasonable amount of someone else’s work in your thesis you may need to ask for permission.
If you are using a whole work that belongs to someone else you should seek permission. This could mean you are using an image, a photograph, a poem or a map, it doesn’t have to mean an entire article; these standalone items are considered to be whole works.
Asking for permission really comes down to individual judgement - you need to determine whether you’ve used someone else’s work beyond the permitted exceptions and need to seek permission. It’s a personal responsibility.