The various forms of naturalisation which persons who live abroad can apply for are described below (the Articles cited are from the Nationality Law).
The procedure to file an application is explained at the end.

Article 28 states:
"A foreign spouse of a Swiss national who lives or has lived abroad can submit an application for simplified naturalisation if he/she:
a. has been married to and living with the Swiss national for six years and
b. has close connections with Switzerland."

The requirements in general:
Since 1 January 1992, men and women have been treated equally when they marry a foreign national. Thus, on the one hand a woman with foreign nationality does not automatically acquire Swiss nationality through marriage to a Swiss national. On the other hand the foreign spouse of a Swiss national (man or woman) can submit an application for simplified naturalisation to the relevant Swiss mission under the circumstances mentioned. Besides six years of matrimony the Law requires the applicant to have close connections with Switzerland. The following conditions must largely be met, either cumulatively or individually:
a. holidays regularly spent in Switzerland
b. close contact with Swiss Clubs abroad
c. close connections with persons living in Switzerland (particularly with relatives and friends of the Swiss spouse)
d. ability to communicate in a Swiss national language or Swiss dialect.

The effect of the former Article 31, replaced by Article 58c from 1 January 2006, is as follows:
If a child born before 1 January 2006 with foreign nationality has a Swiss father who is not married to the mother, the child did not automatically become Swiss. If the father acknowledges the child before he/she reaches the age of majority, the child can submit an application for simplified naturalisation before reaching the age of 22. After the age of 22, the child can submit an application for simplified naturalisation provided he/she has a close relationship with Switzerland.

Article 58a states:
"A child with foreign nationality who was born before 1 July 1985, and whose mother was a Swiss citizen before or at the time of the birth, can submit an application for simplified naturalisation if he/she has close connections with Switzerland".

From 1 January 2006 the same applies to children of a Swiss father married to the mother who have not been registered with the Swiss authorities before the age of 22. An application for simplified naturalisation can be submitted providing the applicant has close connections with Switzerland. Article 21 applies in such cases.

A Swiss woman who, before 1 January 1992, lost her Swiss nationality by marrying a foreign national - because she did not sign the declaration of intention to retain her Swiss nationality which was necessary at that time and already had the nationality of her husband at the time of the marriage or acquired it through marriage - can submit an application for re-naturalisation if she has a close relationship with Switzerland.

A child born abroad who is a national of another country besides Switzerland loses his/her Swiss nationality if he/she does not register with a Swiss mission before reaching the age of 22 at the latest.

Article 21 states: "A person who, for reasons which may be excused, has omitted to register or to make a declaration as required by Article 10 and who has thereby forfeited his/her Swiss nationality can submit an appilcation if he/she has close connections with Switzerland."

A foreign child who could not become Swiss because the parent lost Swiss citizenship (Article 31b) or had to give up Swiss citizenship in order to acquire or keep a foreign nationality (Article 23) before his/her birth, can apply for simplified naturalisation if he/she has close relationship with Switzerland.

In order to apply for simplified naturalisation or re-naturalisation the correct application form must be requested from the relevant Swiss mission. In addition to the application a questionnaire must be completed and, depending on the case, registry office certificates must be enclosed. The Swiss mission checks the application after it is submitted. In cases relating to Arts. 28 and 58a the applicant comes to the Swiss mission for a personal discussion to allow his/her connections with Switzerland to be assessed. 

Following this the full application is forwarded to the Federal Department of Justice and Police which, as the Department responsible for simplified naturalisations and re-naturalisations, takes the final decision.

The total costs normally amount to around USD 360.00 for all applications. The chancery fees of the Swiss Embassy of USD 120.00 must be paid when the application is submitted; the rest is payable on receipt of the decision.

In all cases the procedure tends to be relatively prolonged, since every application from around the world is dealt with by the same office. You should therefore be prepared to wait for up to two years. Please do not make inquiries with the Swiss mission or directly with the authorities in Switzerland during this period.

The decision together with its date of entry into force are sent to the applicant via the relevant Swiss mission. Once the applicant has been naturalised, he/she will have to register with the Swiss mission competent for his/her place of residence.

If a Swiss passport or identity card is required after the naturalisation, a fee of USD 49.00 for a certificate of civil status, which will be obtained within approximately 4-6 weeks, will have to be paid. No new Swiss travel documents can be obtained for a naturalised person without a certificate of civil status.