How to get lab resources back from a post-doc who resigned while on vacation and not coming back?
The issues you are describing of misappropriation of university equipment, research data and unearned salary, rise to a level of seriousness that a rank and file faculty member is not equipped to deal with and will not typically be expected to deal with. It is time to call in the cavalry — by which I mean, the matter should be referred (probably through your advisor’s department chair) to the university legal counsel or similar office. They will take appropriate steps, starting with sending the absconding postdoc a threatening letter, and ending with who knows what (in theory, a police report and/or civil lawsuit, although given the negligible economic value of the misappropriated items and the difficulty of proving outright theft, I’m guessing not much legal action will come of the whole business).
Of course, I’m hoping that the postdoc will listen to reason and return what he has wrongfully taken, but in any case, if your advisor hands the matter over to the university authorities, and cooperates with the resulting follow-up actions, then even if the items are not returned, your advisor will be in a good position to explain to their funding agency and collaborators that they tried in good faith to fix the problem, and the embarrassment and damage to their professional relationships will be kept to a (probably negligible) minimum.
Good luck!
Your advisor needs to talk to your department's administration and they need to talk to a lawyer.
However, since the person you want to take action against is in another country, you have no realistic hope of gaining a legal resolution (unless perhaps you and he are both in the EU). The cost of conducting and enforcing a legal action in another country is massively, massively higher than the value of the laptop and any salary he was paid.
As for the research data, you'll just have to keep an eye out to see if he does anything with it. He probably won't but, if he publishes anything using the data, you'll need to be able to demonstrate to the journal editor that he stole the data from you, that you should be co-authors or whatever would be appropriate.
It is difficult to apply the needed pressure at a distance. However, I assume that the data is more important to you than the laptop. You might try to make a deal with him that if he returns the data, complete, that you will let the matter drop. It might be just a bluff on your part or not, but it might be your best outcome.
Alternatively, if he becomes associated with another institution, you might be able to work through them (or threaten to) to apply the needed pressure for a resolution.
In the case that you don't actually need the data returned as you also have it, you should inform him, by some sort of registered (governmental) mail that any use of the data by him will be treated as improper and followed up on with "appropriate authority". What you want back is his assurance that he will make no use of it, so you might include an affidavit, to be signed and notarized, to that effect. Make everything as official as possible.
However, since he was a post-doc, presumably you have access to his former advisor and the institution he studied at. You can, carefully, contact them, avoiding anything that can be construed as slander. But you can also threaten to contact them. Unethical behavior in graduates, if known, is not welcomed.
And have a plan in the future for proper backups of important data that is "owned" by the project and not by individuals.