Is this the right way to hold a sai?

The picture of the sai held with the Tsuka forward and the blade along the forearm is correct. The normal grip that has the blade pointing out is to small to tell how the person is holdi8ng it. It appears as if his thumb is not in the correct place. The grip should be such that the fingerprint side of the thumb is pressing against the base of the handle where the handle and the blade meet. The placement keeps the thumb out of the way in case you deflect a weapon and it slides down the blade stopping when it meets the point where the prongs, blade, and handle meet. There are several movies and TV shows that have shown someone holding the handle whit the blade out so that one or two of their fingers wrap around one of the prongs. This is absolutely wrong. Holding the Sai that way means that if someones weapon slides down your blade it will strike your fingers. To clarify, at no time are your fingers wrapped around the prong/s in such a way that your fingers are on the inside of the prong/s.

....

The sai is a trapping weapon as well as a striking and piercing one, just as the site describes (uchi, kake uke, and tsuki). Flipping the sai from a forward position, to an inward position, and vice versa, is how a lot of these actions build power, and a lot of the trapping will happen in the inward position. Neither position is solely defense or offensive. They serve as both.

I am, however, unfamiliar with the position in the three picture demonstration where he's holding the sai at the saki. I have never practiced that, but not to say it's wrong. Different styles have different methods. The only time I've never held them there is when throwing the sai, and that's only for certain distances.

In our style it is not.

For the closed Sai, the long part of the Sai should be along the outside of your forearm (along the ulna) so you can block not underneath the arm.

The Sai should also be tight against the forearm and there should be no space between the Sai and the arm the whole length of the Sai, again for blocking purposes.

For the open Sai, I agree his thumb is slightly off and should be right on the X where the blade and handle meet.

Just looked at the blocking pics further down and noticed his Sai in these pictures are held correctly, because the blocks don't work if you hold them incorrectly as in the pictures above. Don't know why they are held incorrectly in the first few pics.

Finger placement is correct on the closed Sai, thumb on one side, forefinger on the handle and the other three fingers on the other side. Only the Sai is placed along the ulnar and not along the underarm in our style. I know of no traditional style who teaches holding the Sai between middle and ringfinger, even Shotokan. You sure you understood this right?

Sorry, I meant between the middle and ring knuckles*

the link goes to an article with multiple pics

second get an instructor in sai-jitsu

Huh?