There's a problem with that. There's a problem with that too because the context does not say that. So Thomas saw clearly that Jesus was God. Now here the Witnesses will think you're falling into their trap for they have a different translation. Well, the first thing to do is to show them that both translations can't be right.
Someone is wrong.
The truth is only one would, theirs. If they're honest, they'll think about it. Then you take their Bible and count the number of gods with them. This is where they get stuck for they must either say two gods and be polytheists or deny their translation. These are two great verses to use when witnessing to Jehovah's Witnesses.