Resizing a window by dragging its side is disabled if the window is perfectly aligned to the edge of the screen. So with some more precise placement of your window, you will achieve the effect you want. You just need to "snap" your window to the right edge.
Try it as following: click and hold the mouse button on the title bar, and drag your window to the right. When it touches the edge of the screen, it will "resist" a little bit. If you continue the drag, the window will go past the screen. If the mouse cursor approaches the edge, an orange highlight will appear, indicating that the winow will be tiled when released.
In your case, release the mouse button at the point where it resists a bit. Now, the window is snapped to the right edge, and it will work like you want.
The same effect happens when you tile the window to the right half, or full screen.