Switch – Installing an insignia connect smart switch to three black wires and a bundle of three white wires

The black wire that goes to multiple switches should be your hot leg. If the black wire in the back is on the same side (top / bottom) as the wire going from the screw to the other lights this is the line and it will need to be connected to the other switches and your new one or they will no longer work if capped off if that is the case the other wire is the load. The whites are the neutrals when bundled (some times in a switch loop a single white can be hot, they are supposed to be marked but many times they are not).

Your fan is designed to be internally self-switched using the wireless remote. As such, it's looking for 3 wires:

• Equipment safety grounding/earthing, which is always green or bare (even in Thailand)
• Hot (of some kind), a current supply, which can be many colors
• Neutral, which is a current return, which must be white or gray. (white wires are often not neutral).

Grounds are easy because all grounds get connected together in every case, unless you're doing extreme wizard-work in a test lab, audio studio or factory.

When you see two cables entering, and both blacks are already tied together, and both whites are tied together, that circuit is carrying current onward to some other point-of-use. "It's not yours to disassemble" is probably the best way of thinking about it. We have another question today where someone dismantled one of those, and it turns out it also served his neighbor's apartment.

However, you can tap it, by adding your own wires to the bundle. Usually when it's a simple 2-black and 2-white (or 3-3, 3-4 or any nearly equal number) in a bundle, you can count on the whites being actually neutral. So voilà, we have found where to attach your fan's neutral wire: add it to the bundle.

We don't quite know what those black wires are. They may be always-hot; they may be switched-hot off a mystery switch. It would help if we knew where the onward wires go, because builders don't install wires unnecessarily. Regardless... these are the only "hot" wires in the box, so they are our only choice for the fan. The fan's black wire gets added to this bundle.

That's the best we can do. Expect one of your do-nothing switches to start doing something. This may not play well with the remote.