Exactly what I said. You need to obtain Thai permanent residency first, which you can apply for after a full three years of uninterrupted work permits. After holding PR for 5 years, you will then be eligible to apply for Thai citizenship. It's a very long process of 8+ years. If you are not already working here you have no chance!
If you are single or not married to a Thai national, you need to obtain Thai permanent residency first, which you can apply for after a full three years of uninterrupted work permits. After holding PR for 5 years, you will then be eligible to apply for Thai citizenship.