Will frequent short stays in Thailand raise immigration concerns?

yes depending on the immigration officer. But, I think yes. it can be problem. immigration officer are trained and educated when they started to work as immigration job as others do almost the same for their jobs. Their process of finding suspecting someone is just normal as normal people can think. For example, you are in 20 or 30s.. and from USA. Normal people in this age have jobs and works regularly. Maybe once a year to visit Thailand for vacation is very normal and stay for few weeks is normal too. But three times a year visited Thailand? They surely can ask, do you work? if yes, where to work? what company?? and what job? How much salaries?? Normal people in age 20.30 can not make such long and often holidays from the company? That is actually not normal. If you work remotely? you do not have to go to company every day? yes, then DTV is an option. or if you are so rich? early retired? yes why not? LTV or elite visa are the options for you. If you are over 50? and retired? and visit often Thailand? stay long there? yes, retirement visa is an option too. If your company is so generous and does not care how often you are off or on, and pays well regularly. And you also have enough budge to enjoy in thailand. Just show your budget and bank statements with good explanations. then, you will have no problem. It is not so normal but just unique case.

Less than 180 days a year along with no extensions past 60 days should be acceptable as a 'genuine' tourist

HOWEVER

It is up to the individual immigration officer each and every time you enter.

No problem

Last week they stopped me 10 minute interview. I am not a tourist she tell .. I got in but next time I need visa

Depends who stamps you in. At some point they will say you are not a tourist

It will always depend on the Immigration officer. If you want to be sure, obtain a visa appropriate to your reason for stay.