Can I use 24 gauge speaker cable?

@sjeesjie the answer you're really looking for is the following:

There is an audible difference in wire.  Gauge/Quality/Connectors all play a factor.  

You can VASTLY improve audio quality by spending a $100 or so on HIGH quality cables of the required length/connector.  

I did this a year ago.  Upgrading from some 12ga "monster cable" stranded wire, to some 8ga stranded with bonded banana plugs, and was absolutely floored with the before/after.

All of the above get's magnified as you increase other components in your system.  Do yourself a favor, spend a few bucks now.  It's worth it.

If Paul W. Klipsch stated in his time, lampcord would be quite adequate for speakers, great selection at Home Depot, but probably cheaper at Walmart......

Can you use 24 awg? Yes
Do a simple listening test. 14 awg from Amazon or the depot. Then try the 24 awg. See what sounds better.... No Brainer.

It is a little too thin.

Probably not suitable for an amp with more than 10 watts/channel output.
When the wire is too thin, its resistance will be relatively higher and its stray capacitance tends also to be higher. This would limit the current flow and affect the high frequencies negatively by attenuating them.

If you have an amp with any power output greater than about 10 watts/channel, you should probably use approximately a 16 gauge wire. Having said that, you do not have to buy any esoteric expensive "audiofool" wires. Any ordinary pure copper wire (NOT copper clad or aluminum) will do. Just make sure its capacitance is as little as it can be.

All in all, you should not need to spend more than 30-40 bucks on it, AT MOST.

This would do PERFECTLY for example:

https://www.amazon.com/KnuKonceptz-Kable-Gauge-Copper-Speaker/dp/B006VP97DE/ref=sr_1_4?dchild=1&...

or this....

https://www.amazon.com/InstallGear-Gauge-Speaker-Wire-Oxygen-Free/dp/B01MQVETL7/ref=sr_1_1?crid=3A20...

#24 AWG seems to be thin. 5m is long.
Front or rear speakers?
to get the front speakers cable thickness I need your Amp's Damping Factor (DF).
Then I can calculate the thickness (AWG) with the 5m length.