I say that because if you get a different Immigration Officer on the way back he may not have the same opinion as the one who told you to get a tourist visa.
If you were denied at the end of January there is a good chance of denial again based on why they denied you the first time. But of course this is Thailand and who can say for sure.
I agree with most if the comments. But important questions need to be answered like his age, also are you in Thailand or will he live by himself? How is his health? Does he have medical conditions that need care because Thai Insurance companies generally do not accept people with pre-existing conditions and if he is on Medicare it is pretty much useless unless he has like maybe a Medicare Advantage Plan that will pay for someone who lives overseas. These questions should be taken in to consideration before anything else.