Like everybody else he will have to fill in the entry/exit form given to him by the flight personnel before arriving in Bangkok. He will present this form together with his passport at the immigration booth by arrival, and he will get his 30 days stamp in his passport - usually that's that - and he can start enjoying his stay in wonderful Thailand.

Tell him to keep the exit slip of the form given back to him by immigration carefully with his passport, or he might have problems by leaving the kingdom.