These US visa types are for those who have children and wanting to take them to the US while their mother has a K1 fiancée visa or a K3 spouse visa. Usually the attorneys in Thailand would start the process together with the other application for the mother. Below you will find the basic break down of the visa types and advantages.
The K2 visa is where the mother has applied for a K1 visa. The child’s name needs to be on the I-129F petition when the process starts. You attorney will ensure that this is done when you start the process. Once the mother has married the child needs an adjustment of status by completing an I-485 Application to Register Permanent Residence. You will not require a separate petition if the child is going to follow the mother within the space of a year. If this is not going to happen then a separate application needs to be done later.
The child needs to be under the age of 21 and must be single. Note that the visa is approved at the same time as the mother and it is cheaper to do them together than to file a separate petition a year later. The child will be allowed to study while in the US on the K2 visa.
This is a visa where the mother has applied for a K3 visa. Much like the K2 visa the application is done at the same time as the mother’s application. The child needs to be single and under the age of 21. There does not need to be a separate I-129F application much like the K2 visa.
If you are not certain what you need to do then contact a lawyer in Thailand for more guidance and advice. The process needs to be done properly and it is best to seek legal advice in immigration matters. Errors can be costly and cause lengthy delays.