There has been a couple of posts of people being questioned about why they got their DTV in xyz country and not their home country but I don’t believe there has been any mention of actual denials.
You can’t renew a tourist visa. With one you’d get 60 days on entry.
Most nationalities can extend that once for 30 days.
I suspect you may be referring to border bounces where you briefly leave Thailand and return for a fresh entry stamp.
If so the answer is that there is no official limit. It’s up to the immigration officer to decide if they will let you in.
They are getting tougher on these so if your relative wants to do this then probably best to use an experienced border bounce company as they generally ensure you can get back in.
It’s the date of your last entry in to Thailand. If that was in November’23 then put that date. If you’ve since been out and returned then put the date you last entered.