Son had an apartment there some years ago, he was single with no responsibilities and enjoyed traveling so why not.
We traveled there at a different time, it's like any other large city.
You need to aware of pick pockets.
Take multi copies of passports and credit cards
Use money belts.
Don't use Internet cafes if at all possible. If you need to use the Internet use the business section of a good hotel, it's probably more secure.
There are some amazing sites in and around Bangkok and it's well worth the extra caution.
A lot of it is just common sense, the only time I had something stolen was in Quito Ecuador, a top which I had folded over the straps of my backpack. It was so quick these people are professionals at stealing.
Go see your son and enjoy the visit.