NP - Even remotely it could be an issue. My old Japanese company registered in Thailand would allow WFH but still needed a WP if employed by the Thai legal entity.
Singapore Embassy have always need to be known to be a bit "Awkard" though for certain visas. They are great for "B" Visas for work though - very efficient
As you say. Proof of Residency ie long term visa. Look at how Singapore has handled this for decades. You need to be a Singapore Citizen, PR or on other long term visas to apply for certain Thai visas there. You cannot apply for a DTV on a short term visa such as tourist.
The Immigration Offices are run like little medieval fiefdoms with the local head having power. What may be profitable in one area might be different elsewhere :-)
Majority of visitors are probably not aware it exists. Then each office has its own rules that they change on a whim. Jomtien pre-covid started asking for re-registering after any trip away from home. Then that was too much work so just overseas trips. Stopped it altogether. Brought back re-registering after overseas trips last October - and ended it again a month or so later. When I was on a BOI Visa from One-Stop-Shop in Bangkok it was never needed. I asked in my office about it as they dealt with all foreigners immigration and they had never heard about it or done it for any of the dozen+ foreigners. Nobody ever had an issue with 90 day reporting, renewals etc. "This is Thailand" :-)
A few months ago at Jomtien I had to help a French couple trying to do 90 Day. They were in friends condo and no TM30. The Immigration Assistant was trying to tell them to get TM30 first but was not getting through. I think they wanted extension too but needed the it for that as well.