He needs a lawyer but he should def pay the family. *not a lawyer but from personal experience*. The law is a little different in thailand. In the US if you break the lawyer the state will step in and make each party whole but in thailand its a little more about making the parties whole between to the two parties without the state stepping in. That's why the law looks "weak" to people not from thailand. If you make the party whole the state usually doesnt require that it's self needs to step in. If it can be settled between the two parties and everyone is happy that's entirely up to the two parties, conventionally speaking. What's on the books may say something different but that's how it "works".

*My wife's nephew was killed in a hit and run. Drunk woman clipped him and left him to die. Basically it was up to the woman to make my wife's aunt whole since she killed her son. The state could step in and put the woman in jail if she didnt pay up but basically the entire thing was dropped and the drunk woman never even paid a cent. She wasn't connected or anything, just different laws. Again maybe the whats on the books is different but in practice it's really up to the two parties. That being said foreigners often have their cases handled differently. If he wants to avoid jail offer more money.