get robbed in Thailand

I even don't know when and where it's happened. But they must have had loads of time to do that, as they've taken only one of my cards even thought they were in one place and the same with money, they've left some so that I would not discover it to soon. They must have dig through all my stuff and be able to open bag, which was in bag, which was in another bag.
And indeed I did not discover it until next three days probably. Just before leaving from Bangkok to Vientiane. So imagine how surprised I was to find out that I'm 400$ short and my Amex is gone.
Luckily I've managed to deactivate it, but that was a bit of challenge as well, as my phone was locked in another room, where I temporarily had no access, so I had to find someone to do it for me from Poland. Kinga as always was helpful and managed to call them and even get some details on transactions performed. Which was 300$ in Tesco in Thailand.
After I got my phone back I gave them a call once again to ask more details, like which Tesco or what time the transaction took place, but the only thing that they knew was time - 21 American time on 24th of December, which here is about 9a.m. on 25th of December.
I've arrived to Bangkok by bus very early morning on 25th and took a cab to the guest house, where I went directly to bed and locked my valuables before. Maybe it was my mistake not to check it before, but still that probably would not help, cause my idea is that the robbery occurred on the bus.
Many people say that it happens very often on the bus. They spread something to make you sleepy via air conditioning system and than go through your bag.
So my journey to Laos has started in a bad mood. I also started to be suspicious and maybe paranoid sometimes. I've lost this security that I had so far.