It's a small Mitsumaru brand table lamp from HomePro with a metal base and lampshade. It has the box-in-box symbol on it, but inside I see there is nothing between the wiring and the metal base. I thought there was supposed to be a plastic barrier to make it double-insulated...

PV jacketing and shrink tubing on the wire probably makes it double insulated.

Well, the jacket on the wire is presumably the first layer of insulation. How about the second?

I thought double insulation was to prevent wires that have come loose or frayed inside from touching the metal case. With this lamp - say the live wire going into the switch came loose, then it could easily touch the metal base of the lamp because there is no second layer of insulation such as a layer of plastic between the wire and the metal base.

If this lamp is technically double insulated, then I guess I never really understood what the term meant...

Well, the jacket on the wire is presumably the first layer of insulation. How about the second?

The jacket on the cable is the second insulation layer, the first is the plastic covering each of the conductors inside the cable,

It's certainly marginal for being classed as double insulated, the switch for example has only a single insulation layer.

But in reality, if combined with an RCD it's quite safe.

Mitsumaru appears to be a Chinese company that has given (copied for) itself a confidence inspiring Japanese name.

Nice use of rough worked timber/balsa wood and expanded polystyrene.

Do you enjoy playing Russian Roulette?

@Enoon. I see no polystyrene (it's a cement weight).

I don't see an immediate hazard, at worst it's unsafe rather than dangerous.

If worried nothing to stop you installing a 3 core flex and grounding the metalwork.

The biggest danger may be that dang Europlug - they just do not make good contact in most Thai electrical outlets and if pushed in fully often do not make contact or can arch becoming a fire hazard. In proper outlets agree they are fine and help prevent external contact to live wire - but in Thailand they are a source for frustration.