Hi, I plan to visit Singapore next Saturday for the next Barcamp event and I want to know what I should do to go there. I am French and am married with a Thai woman which allows me to stay in Thailand for one year with a non-immigrant visa.

As a French citizen, I don't need a visa to go to Singapore but I think I need to notify the immigration office I will leave the country for a few days if I don't want my Visa O to be invalid when I come back to Thailand. Could someone confirm this or tell me where I can find the information ? Should I buy the airplane ticket first? And last question, how many days does it take to get everything in order?

Thanks.

I think you are on 1 year extension based on marriage.

You need to go to Immigrations and get a Re-entry permit.

1000 baht for single re-entry.

3800 baht for multiple re-entry.

When you come back from Singapore, state the re-entry permit number in the visa number box on the TM.8 (arrival card)

Agree with the above if you are on extension of stay obtained at Thai immigration (it is not a visa). You would need to obtain re-entry permit from your local immigration office. Note that on re-entry into the Kingdom the count for your 90 day reporting will start again, the day of re-entry counting as Day 1.