You're very right. Some people do say that, and it could be. It's hard to know exactly what the "mark" will be, so we try to be alert and watchful for the Lord's return.

What some people said is the mark of "666" is demonic mark of identification of satanic followers amd this mark will come after rapture.

If the tattoo is a mark of a demonic creation or of a religious devotion, as the 666 would certainly be, it is forbidden, just as in the book of Leviticus. But we don't know what kind of mark the "666" is. Revelation 13.16 doesn't specify what the mark is. Some scholars think it might be a branding iron brand, some think a tattoo, and others think it's a metaphor for pledging allegiance to the beast and it won't be a literal mark on the hand or forehead. It's not specified, so I can't guarantee you that it's a tattoo.

Since it is the mark of the beast, now please tell me the different between "666" as the beast mark and "tattoo" as a mark.

Yes it is. It's the mark of the beast.

For example, the mark "666"—is it not an evil mark or demonic mark?

Right, but we have to understand what the writer meant by what he said, not to make it mean what it means to us. It means what the person who wrote it meant it to mean.

Let me give you an analogy. Suppose you are a parent, and your son is hitting your daughter, so you say, "You are not allowed to do that." OK, so the next day, your daughter is digging a whole in your yard, and your son says, "Mom said, 'You are not allowed to do that.' " Well, you DID say that, but it was a different situation, and you didn't mean "Don't dig in the yard" when you said it. You meant "Don't hit your sister."

So we have to know what the writer meant by it when they said it, not the way we want to apply it. Does that help?

I also asked some religious leaders, and they said, Once a law is always a law, and that is what the Scripture says so we have to obey it.

I asked an Old Testament expert. He said, "The prohibition against marking the skin may involve either tattooing or painting the body as part of a religious ritual. Such markings may have been designed to protect a person from the spirits of the dead or to demonstrate membership in a group. Some evidence for this has been found in the examination of human remains in Scythian tombs dating to the 6th century BC. The Israelite law may prohibit this practice since it involves a self-imposed alteration of God’s creation, unlike circumcision which is commanded by God."

The commentary by Gaebelein says, "There was nothing morally wrong with tattooing. These practices were part of heathen rituals, and that was the problem."

Another commentary said, "It is probable, from the association of verse 29, that a strong propensity to adopt such marks in honor of some idol gave occasion to the prohibition in this verse, and they were wisely forbidden, for they were signs of apostasy, and, when once made, were insuperable obstacles to a return to the true God. This practice is possibly referred to in Isaiah 44.5; Rev. 13.17, or Rev. 14.1."

Somebody else said, "This refers to the disfiguring of the skin, probably with the emblems of pagan deities, dishonoring the divine image in a person, and was forbidden because it did not reflect God’s holiness. See Dt. 14.1-2."

So that's what I have and what I know. It's the idea that that's what it MEANT. Their rule about tattoos was not just about marks on the body, but about religious rebellion against God.

Okay, for us to prevent ourselves from sin we have to obey what the Scripture says, do you know why? Because the scripture did not say that it is the mark of the evil spirit.