Is it safe to use the THIM app for Thailand immigration?

There have been multiple threads on Reddit and Facebook about this new mobile app that was allegedly released by the Thai government, but in the app stores it is owned by a crypto company called Hashpays:

According to their own press releases, it was a third party company called Digital Identity Co., Ltd. that helped develop the app, not Hashpays. Some of the users who mentioned this on Reddit were immediately mass-flagged as spam by the infamous "visa agent sock puppets" and had their account banned as a result:

https://www.reddit.com/r/expatsinbangkok/comments/1tuwlsm/who_developed_the_thim_thai_immigration_mobile_app/

https://www.reddit.com/r/Thailand/comments/1tut2ip/a_crypto_exchange_developed_the_new_thai/

Who really controls this app? It is collecting passport, health, and personal data on millions of tourists heading to Thailand, so it would be nice to clear this up for safety reasons.

The app is indeed an official government app (see here or here) . A good overview of what it does and doesn't do at the moment is here: https://www.youtube.com/watch?v=H89wm1CkVe8

Most importantly, you will still need to fill out your TDAC before arrival

Since TDAC is still required and (at least the last few time I did it) is a reasonable process, I really don't see what the THIM is actually good for. It's currently "in pilot" and "more feature might be added" but so far I see no reason to use it all.

Maybe this whole thing is a similar project to the infamous Thailand ETA requirements which was announced repeatedly with great fanfare but than delayed, postponed, delayed again, and then quietly fizzled out.

Who really controls this app?

If you want the legal answer, you would need to read the terms and conditions. It IS an official government app but cronyism and corruption in the thai government are not unheard of.

It is collecting passport, health, and personal data on millions of tourists heading to Thailand,

Only from people who voluntarily download this app and provide the information.

so it would be nice to clear this up for safety reasons.

The safe path here is easy: just don't use it. Ignore it until its either useful enough to be worth the bother or it becomes a legal requirement