I wanna know, because I got a 20w solar panel kit that I got for Christmas from my brother, and I wanna know if thermostat wire can be buried underground. Because I'll probably do a temporary low voltage (mostly 12VDC) lighting system in my backyard, with a 10ah or 12ah 12V battery, until I get my electricians license to put up some of my streetlights that I'll probably will be getting from LED changeouts, and possibly ReStores.

Plus, I know that thermostat wire is sunlight resistant, but can it be buried?

I see no reason it couldn't be buried. But I think the wire for those 12v garden lights would be a better choice.

I think a good way to bury low voltage wiring is to put it inside lengths of old garden hose to protect it from the damp of the ground.

Assume we are talking about really an electrical wiring (so the sensor itself is electrical) and not about a capillary tube (where the sensor is a bulb with melting wax or evaporating liquid, connected by a thin tube to the remote placed pressure switch responding to the sensor temperature).
The bulb+capillary+diaphragm termostats assume certain temperature ranges common for their intended use for each component to work correctly (fridge thermostat assumes the bulb to be the coldest, the tube varying and the switch part the hottest; an oven thermostat expects the bulb with part of the capillary to be the hottest, the rest of the tube and the switch the coldest,...). These then may work incorrectly, if the tube will be the only coldest part (a result of it being burried).

@Medved:
Yes, its just normal electric wire, generally 18-gauge,  just sold as "thermostat wire"

I see, you want to use that "thermostat wire" for some ELV electrical installation, correct?

The indoor ELV wires (here these were called "doorbell wires", because the doorbells jut do not need anything better) use to use very cheap PVC insulation, which is partly hygroscopic and corrosive (release chlorine mainly when heated, PVC in these does not contain that efficient stabilizers as the mains rated wires do), they are really intended only for indoors.
I dont think a garden hose will help with the humidity. Mainly in hot days water may condense and collect in the underground parts of the hose (unless there is some drainage) because the ground there will be colder than the air picking up humidity above the ground.

The only good service the hose will provide is a kind of marking (when you will be digging something else there) and as a conduit allowing the wiring to be rather easily replaced once it falls apart.
Otherwise for a more permanent installation, I would definitely go for an underground rated cable, even for 12V wiring. It is just because the insulation plastic composition is designed to hold up in the ground environment...

I think a good cable to use is the direct bury rated low voltage lighting cable which I believe is fairly cheap compared to UF cable.

I think a good cable to use is the direct bury rated low voltage lighting cable which I believe is fairly cheap compared to UF cable.

Well exactly, its a 18AWG cable.