How can I extend my Non-Immigrant O Visa in Thailand without leaving the country?

My advice would be to contact your local immigration office and request the handout for a one year extension of stay based on marriage to a Thai national. Different immigration offices have different requirements, but expect to show the following:

1. The applicant’s passport and a copy of:

a. The data “picture” page.

b. The most recent visa (if applicable).

c. The most recent entry stamp or extension of stay (if applicable).

d. The departure card (“TM 6”) that should be stapled in the passport.

2. The extension of stay application form (“TM 7”).

3. A copy of the submitted Notification of Residence of Foreigners form ("TM 30”).

4. The Thai spouse physically next to the applicant, and;

- Their Thai ID card and a front and back copy of the ID card

- Their housebook, and a copy of the first page.

5. For male foreigners married to a Thai female only:

- 400,000 THB in a Thai bank account, seasoned for 2 months OR;

- 40,000 THB in income OR;

- A letter from the applicant’s embassy stating the applicant has an income of 40,000 THB a month. If the embassy offers the income letter, the income method can not be used.

5. Marriage certificate (either the rose border certificate, OR a translated and certified copy from the applicant’s home country issued by the Ministry of Foreign Affairs), and a front and back copy of the marriage certificate.

6. An updated Kor Ror 2 showing the marriage is current, acquired from the local amphur office for 20 THB.

7. 2x passport sized (4cm by 6cm) photos.

8. 1,900 THB processing fee.

Different immigration offices have different requirements, and may include:

- A hand drawn map to the house.

- Pictures of the husband and wife in various locations in the house (front of the house/ condo, in all rooms, etc).

- Rental contract (if renting property or a condo).

There is an under consideration period for this extension of stay. This may include an at-home visit by the immigration office to confirm the husband and wife are living together, interviews with neighbors, and if using the banked money method, to confirm the money is still in the bank account. The immigration office will give a list of the documents required to bring when the under consideration stamp is closed out.

You also need a re-entry permit to keep the extension of stay alive, so you won't need to go through the process again. This keeps your stay alive to the "admitted to" date.

To acquire a re-entry permit, the following documents must be submitted to any immigration office or at certain airports:

1. The applicant’s passport and a copy of:

a. The data “picture” page.

b. The most recent entry stamp or extension of stay.

c. The departure card (“TM 6”) stapled in the passport.

2. The Application for Re-entry Permit (“TM 8”) form.

3. 2x passport photos.

4. The fees of either 1,000 THB for a single entry permit or 3,800 THB for a multiple entry re-entry permit.