Visa are not renewed. What new visa will he be applying for?

There are better choices to get a visa than Phnom Penh.

There are direct buses from Bangkok to PP. It is number 13 on this list: http://home.transport.co.th/index.php/th/2014-12-16-07-24-56/%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%A7%E0%B8%A5%E0%B8%B2%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96/item/443-%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96%E0%B9%82%E0%B8%94%E0%B8%A2%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%A3%E0%B8%B0%E0%B8%AB%E0%B8%A7%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B9%80%E0%B8%97%E0%B8%A8-international-route.html

the guys are going to obtain Non-B, with the letters from their new employer,

My son is 18 with double nationality, Canadian and Thai. Last year he went by van from Trat to Siem Reap and they got rip off just before the border, the Thai driver stopped and asked for more money from all of them in the van.

They told him that they did not know that he was Thai, they said that their business was to make money with falangs and if they had known that he was Thai they would not have taken him. It was you pay or you stay here on the highway.

May I suggest that you fly instead or take the visa run bus from Bangkok.

Yes, I would agree this option too, less hassle,

Visa are not renewed. What new visa will he be applying for?

There are better choices to get a visa than Phnom Penh.

There are direct buses from Bangkok to PP. It is number 13 on this list: http://home.transport.co.th/index.php/th/2014-12-16-07-24-56/%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%A7%E0%B8%A5%E0%B8%B2%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96/item/443-%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96%E0%B9%82%E0%B8%94%E0%B8%A2%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%A3%E0%B8%B0%E0%B8%AB%E0%B8%A7%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B9%80%E0%B8%97%E0%B8%A8-international-route.html

the guys are going to obtain Non-B, with the letters from their new employer,

Let us hope the guys have more paperwork than a letter from their new employer.

http://www.thaiembassy.org/phnompenh/th/services/1435/21865-Non-Immigrant-Visa-B.html

Visa are not renewed. What new visa will he be applying for?

There are better choices to get a visa than Phnom Penh.

There are direct buses from Bangkok to PP. It is number 13 on this list: http://home.transport.co.th/index.php/th/2014-12-16-07-24-56/%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%A7%E0%B8%A5%E0%B8%B2%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96/item/443-%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B9%80%E0%B8%94%E0%B8%B4%E0%B8%99%E0%B8%A3%E0%B8%96%E0%B9%82%E0%B8%94%E0%B8%A2%E0%B8%AA%E0%B8%B2%E0%B8%A3%E0%B8%A3%E0%B8%B0%E0%B8%AB%E0%B8%A7%E0%B9%88%E0%B8%B2%E0%B8%87%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B9%80%E0%B8%97%E0%B8%A8-international-route.html

the guys are going to obtain Non-B, with the letters from their new employer,

Let us hope the guys have more paperwork than a letter from their new employer.

http://www.thaiembassy.org/phnompenh/th/services/1435/21865-Non-Immigrant-Visa-B.html

Thank you, the link is so helpful,,