My baby was born in Thailand but we are due to fly overseas in May. When we re-enter, is it preferable for him to just enter on a visa exempt and overstay, or for me to get him a visa in advance?

We are both on British passports and I have a Non-B with work permit.

My lawyer says he can just overstay as no penalty, but I want to ensure this doesn't have any negative implications for the future.

Thanks!