Hello, I've two kids from a relationship, the mother is gone sadly.

I've almost no family and her family cannot take care, she's not Thai.

 

Since I'll go to Thailand. There's some special place or nanny can provides a full-time care in some place ?

 

Since, I've to work, etc.

If the kids at non Thai they need a visa for Thailand, oldest one can get one for going to a school (which is needed), the youngest one needs to be your dependent and require official paperwork that it is your kid. 

When you are in Thailand it shouldn't be a problem to get a nanny.