Many expats invest in property and take care of rent collection and various maintenance issues.... does this require a work permit?

According to the law yes. A company would need to be set up to do it legally.

investment not so much and instructing workers to do maintenance most likely would not be a issue. Collecting money showing rooms to customers is a no no

This seems to be a non issue for nearly everyone, I have heard first hand of people getting visits from immigration from nasty snitches and nothing ever came of it the officers didn't really want to be there.........but if you feel the need:

Choose a suitable person.

Issue each year a one year non-registered usufruct allowing that person all permissions to fully run a renting business.

That partner or agent needs to renovate/advertise/communicate/viewings/sign rental contracts....all you do is own the property and receive funds minus the consideration agreed on.

(This may in fact be a more pleasant arrangement than doing it all yourself)

You may be surprised that unlike many situations where you would not expect to pay tax until the initial outlay has been retrieved, income tax is indeed payable. Happily if you want to be one of the minute number of people paying tax on property investment the taxes are pretty low after a host of allowances especially if you have a Thai mum/life insurance etc (before all your tax free allowances there is a blanket 30% income reduction for expenses involved in renting and maintaining property). If a profit-sharing agreement is made with your "chosen person" you will each stay in the lowest possible tax bracket.

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investment not so much and instructing workers to do maintenance most likely would not be a issue. Collecting money showing rooms to customers is a no no

bull**it of course xou can show rooms or houses, how long you are the owner you can do, and you can also collect rent,

you do not need a work permit for investment

I have invested in my business. Will save on work permit costs next year then.