Our son, now 24 years old, is a dual citizen. Thailand and Canada. He left Thailand when he was 10, and has only returned for holidays. He has been going to school and working in Canada since then. He would like to return to Thailand on his Thai passport, and stay for an extended period. But he is not registered for the draft, has not received the letter, and has had no contact with the military at all. I know that the Immigration department have no connection with the military, and do not check a person's draft status when entering the country. I know that if he wanted to work, he would have to show his draft status, but is there any other way that the military would even know he is here? Thank you. 

Do not take the risk, travel on the Canadian passport.

Have a read here https://www.thaicitizenship.com/thai-military-service/

 

Once he turns 30 years old then I think he is exempt, but do check.

Is he registered in a house book? The draft is drawn using that database, and notices would be sent to that address.

 

For many jobs he will not have to show his draft status. Most commercial companies are not interested.

 

He will, however, need a Thai ID card, and to get an ID card he will have to be registered in a house book.

 

The best advice would be for him to not discuss it with anyone in Thailand, as his problems will more than likely arise from someone he knows calling the draft office rather than the draft officers finding him.