- lex soli: By birth in the Thailand to a parent who is a Thai citizen at the time of the birth, or to a parent who is settled in the Thailand
- lex sanguinis: By descent if one of the parents is a Thai citizen otherwise than by descent (for example by birth, adoption, registration or naturalisation in the Thailand).
- By naturalisation
- By registration*
- By adoption
- born in Thailand and living in Thailand until the completition of secondary education
- stateless person entering Thailand under the age of 5 and being in Thailand until the completition of higher or vocational education
- any person living in the country for fifteen years with the prospect to remain resident in Thailand
- a person married to a Thai person and resident for at least 15 years
2. The Thai state is to grant asylum for anyone entering the country to anyone who is suffering political suppression.