Even if they continue getting class S contributions up to age 66 they will have a problem using their S class contributions to qualify for 65s benefit. They will meet the rule to have 52 class S in their 63rd year, but they would also need to have ceased self employment somewhere between age 63 to 65.
If they have some other form of self employment (say for instance they were a plumber) and they ceased this employment they would qualify for 65s benefit.
If their only "self employment" is their ARF they might manage to qualify if they exhaust their ARF before their 65th birthday. I would not chance this because the wording tends to imply that they need to cease their main employment and this might not apply to ARFs.
All this is impractical for a person with an ARF and no other self employment.
If the person you are talking about is an ex PAYE worker, their best method is to qualify under the class A system. They should sign on for class A credits and continue claiming credits at least until the end of the year of their 63rd birthday.
It is allowable to be paying class S Prsi and claiming class A credits at the same time.
They will then just need 13 weeks of paid class A Prsi contributions to qualify for 65s benefit. These 13 weeks must be in the same calendar year. They can be in the year of the person's 61st, 62nd, 63rd, 64th or 65th birthdays.
So to answer your question, they most likely need to work again.
13 weeks of employment with minimum earnings of 38 euro per week will be needed.
3 hours work per week on minimum pay will suffice.