All of what I know about customs and immigration databases, has been due to my acquaintences (immigration officers, or friends who used to build the passport readers, or used to write the software), but I think if you do a determined google search, you will get a hint as to what is out there.
For the first time, I searched google for "customs immigration database" and came up with the links below. (I've never looked for this stuff on the internet before). The trouble with an Internet search like this, is like any intelligence gathering effort, it can be hard to separate the wheat from the chaff. These URLs are not always completely on the mark, as to what is really happening. And the same goes to what a person like me hears from friends (in the security business). They have secrecy constraints on them, as to how much they can reveal. ...
Anyway, here are two URLs that may provide a small hint as to what is going on. ...
Words from a Canadian Auditor General report, complaining not all border stations were properly using the database:
http://www.oag-bvg.gc.ca/domino/repo...30405xe06.html
Database of Doom. A rather biased post (possibly by a bunch of Canuk's who love cannabis), but it does touch on some facts:
http://www.cannabisculture.com/articles/2667.html
Again, its hard to get to the real truth, due to security aspects. But I would be cautious if one thinks this database has only suspected terrorists and suspected drug smugglers in it. They put EVERYONE in it, and then flag everyone as they feel appropriate. If a snarky comment means a customs or immigration official dislikes someone, then they can easily put an unfavourable statement in the database that has nothing to do with drugs nor with terror. The "drug smuggler"/"terrorist" statement, is strictly the "front" justification given by the politicians and by the civil servants to use, to fend off any public criticism of an invasion of civil liberties. In fact the database goes far beyond those two areas.
But I digress, standing most inapproriately on a soap box podium, and I must apologize to all, and step off the podium. Overall, I think your advice is good. Stick within the law (as you point out), and have a great vacation. If I may add be polite crossing the border, and there should be no reason for major trouble. Try not to get too annoyed at the occassional unncessary hastle from a over zealous customs or immigration official.
Anyway, 'nuff said on this. Best wishes to all in their return trip through customs and immigration, after having a truely great holiday in Phuket Thailand.