[1] Jus sanguinis via the paternal line requires a submission to appropriate authorities indicating legitimacy of the child, or a DNA test proving a biological relationship.

[3] In 1972, due to illegal immigration from Burma and concerns over communist insurgency in border areas, the Nationality Act was amended to require that both parents be legally resident and domiciled in Thailand for at least five years in order for their child to be granted Thai citizenship at birth, and revoked citizenship from many people who had it under the earlier act.

[4][5] This caused difficulties for members of hill tribes in border areas who were not registered in the 1956 census, since they had no way to prove that their parents were Thai as opposed to having entered the country as refugees.

[11] The strictness of Thailand's requirements for naturalisation have varied over the years, beginning with fairly loose restrictions, which were tightened in the mid-20th century before being loosened again.

More than half of the naturalisations occurred in 1943 alone, during the Japanese occupation of Thailand, apparently driven by the desire to escape wartime restrictions on foreigners.

[12] Under the 1992 Nationality Act, naturalisation as a Thai citizen requires five years of residence in Thailand, Thai language proficiency, as well as proof of a certain over 80,000 baht income and pay income tax over five years, and a declaration of intent to renounce one's previous citizenship.

Also, a new law allows stateless people to seek employment in professions not explicitly reserved for Thais.

State hospitals now issue birth certificates to all children, a formality often neglected in the past.

However, Section 13 of the current act effectively allows a person in this situation to keep both nationalities, and Thai citizenship is only lost if she makes a formal request for renunciation.