Is there a program similar to the JET program, but in Thailand?

If you are so familiar with the country then you will not need a JET programme or similar to get work there. I'd suggest that with the right qualifications - a degree and a TEFL (Teaching English as a Foreign Language) certificate to get a visa and work - you'll be fine and would pick up work easily, especially as you're already familiar with the country. You could either do this through a recruitment agent or simply by turning up there and knocking on school doors at the start of the school year.