does his father have legal custody? Do you share your child’s last name? Do you appear on his birth certificate? There are 2 issues here. One is leaving the USA. And one is entering/leaving Thailand. Both countries seriously protect children from trafficking and kidnapping. Both immigrations could ask.
You could also write the letter, have it notarized and mail it to him for the immigrations which he will go through alone. This might work unless his father holds sole physical custody.
It’s ridiculous his dad would send him off alone without doing this. I literally got the travel letter notarized in Canada for $15 and took me 30 mins.
Ports of entry in many countries have security measures to prevent international child abduction. If you are traveling alone with your child, you may be required to present documentation proving you are the parent or legal guardian. You may also need a letter of permission from the other parent for your child to travel.
If your child travels alone, depending on the country, they may be required to present a notarized letter from both parents or their legal guardian. If a minor is traveling abroad and is not accompanied by both parents or a legal guardian, contact the embassy or consulate of the country you will be visiting and ask about entry and exit requirements for that country.”
Get a notarized letter from his father stating that your son is allowed to travel on his own and that YOU are allowed to travel with your son without his father/your ex.
Thailand requires this when flying out. If you did a short holiday somewhere you could be asked to present a letter of parental consent for traveling.
Your son may need this for his flight home as well.
Apply for a 60 day tourist visa online. Can extend one time.
If you can get the multi tourist visa better. Then he can stay much longer with exits and extensions.
He NEEDS an exit ticket. Can be by boat even. Just an exit ticket for his first visa allowance.