It says that data was exposed, not stolen.
Supposedly the error was found and corrected before anyone else could access the data. It also noted that no financial or contact information was exposed so there is little risk except that someone may find out something like "John Doe" travelled to Thailand 11 times in 12 months and stayed 10 days each time".
Reading the article, it sounds like a database of the TM-6 Arrival card information.
Not the first time this has happened. A couple years ago Immigration had outsourced the creation of a new database where all foreigners information was stored, including passport numbers and home addresses.
Whoever was making the database secured it with the typical "123456" password which someone else figured out almost immediately. Some of the information was posted on the internet and it took more than a day before authorities found out and changed the password.
There's only a "1point" plan required to get Thailand back on track......get rid of Prayut Chan-O-Chan and his inadequate cabinet! These guys are light weights on the political stage, and now the Biden administration is favoring Singapore and Vietnam over Thailand in the Indo-Pacific alliance...speaks volumes on the success of Prayuts governance!