"Some same thing/person"

My concern is that: is "same" always preceded with "the"?

Yes, "same" is always preceded with "the". This is not always the case in speech e.g. "Same thing here". But this is actually a case of elision of the word "the".

In writing, however, "the" always precedes "same" i.e. "it is same thing" is incorrect, and should be "It is the same thing."

You could however, still use "some", as in:

Some of the same thing/ person

But "the" is still needed to precede "same"

"Some same person" is not correct. You should say "the same person," or "some of the same people."

I saw a person talking with Michael. The same person was waiting for him some days before.
It's no surprise that some of the same people who are willing to pray for rain don't trust reverse osmosis.