Theft from your luggage is unfortunately a thing that can happen. Just like in daily life there are criminals that want to steal what belongs to you. This can surely happen by fellow travelers but also by people who work as luggage handlers in airports, buses or ferry boats. Thailand has seen both arrests of foreign travelers being caught for stealing as well as local employees who work as a luggage handler.
Coconuts Bangkok writes often about this problem. Its like fighting rats; no matter how much you catch of them they will come back.
Phuket airport employee caught stealing Adidas shoes from luggage.
Busted! Baggage handlers at Suvarnabhumi Airport caught stealing from passengers.
Phuket airport staff arrested for stealing from passengers’ luggage.
How people steal from your luggage and how to ovoid theft.
Most common trick is to break open a zipped backpack or suitcase. A padlock wont protect from this since the zipper can be forced to open by poking a ballpoint or screwdriver through it. The following video demonstrated how easy this is done
Also in the YouTube movie with the baggage handler who is caught stealing from luggage uses this method. The padlock that is still closed can clearly be seen. After searching through the luggage he closes the zipper again like nothing happened.
Also the hidden camera footage of police undercover operations in Miami an New York shows baggage handlers, and even a security official, searching through luggage closed with a zipper.
Luggage belt
the above picture appears another suitcase. That one had a extra belt around the suitcase. These are also available with a combination lock on it. Although the are easy to cut through or slip off, they still make it more difficult for the thief to open your suitcase. Most likely he will go for an easier target. Just like in the picture.
That it is not too difficult to remove a closed luggage belt is shown in this YouTube movie.
Zipper-less luggage
To avoid the easily opening of a zippered suitcase you can buy a zipper-less suitcase. This means that the hard shell is closed with a locking mechanism. But sometimes there is a zipper but it is hidden. In that way a thief is also less likely to chose your bag to steal from. The website www.chasingthedonkey.com wrote a nice overview about these types of suitcases.
Flightbags
Another very effective prevention for breaking through zippers is to use a flight cover / flight bag. Even if they are also closed with a zipper it still creates an extra barrier. The thief needs more time to open your bag. Most likely the thief will pick another bag that he sees nearby and leaves your one alone. The company Trafelsafe and Lowland Outdoor sells flight bags that can be closed with a padlock through several rings. Just like a army duffel bag. Big advantage of a flight bag is that it also protects your bag against dust, dirt, water and damage.

Steel protection net
Instead of a flight bag you can also use a net around it. The company PacSafe sells a net made from steel cables that you can close with a padlock. www.bemusedbackpacker.com wrote a review and explanation about it.

Anti theft backpacks
Several companies design special ant-theft bags. The company Pacsafe has a wide range of bags and backpacks with all kinds of features to prevent theft. Where most anti theft bags have a quite complicated design the bags from the company Loctote Industrial Bag Co is plain simple. Just a sack with straps and a padlock. The bags are made out of cutting resistant material and the straps can be used to lock the back to an object so no one can run away with it. Unfortunately they only make day-packs (12 – 13 liter) and no full size travel bags.

Hide your money
When you travel it is always a good idea to keep some cash money with you in Euros or Dollars. In case of a broken credit / debit card or when you end up in areas without ATM’s you can use this to exchange in the local currency. Sometimes hotels offer this service as a side business. To minimize the risk of stealing it is a good idea to hide this. As seen in the first YouTube movie; thieves usually don’t spend much time in searching through your luggage. They grab whatever comes in sight. Some people have developed very creative ideas to hide money while traveling.