Can I extend my non-O visa and my son's while volunteering in Thailand?

Talk to Immigration in Samui - they are there to help - and they will - just be honest and ask them to help you.

Rachel Thompson:

I am quite happy to see your post. I have a single-entry non-immigration O visa as a volunteer as well.

About visa, you need to do a T.M. 30 within 24 hours of entering Thailand, and, before the expiration date, applied and have a work permit. Go to immigration office with your TM 30, work permit, and a report of what you have done in this time period, a report of the place you are volunteering for (IMPORTANT!! Do have someone capable of doing both report for you. The rule for what is required in the report changed couple of times last year. Do know what it is required.) and 1900 Baht. Go to your local immigration office early in the morning, get a cue, and wait for your turn. If everything is done properly, you will get a stamp that let you stay the first 30 days in a 90-day extension. In this 30-day, regional immigration office will send officers to verify your address, type of work, etc. At the last day of the first 30 days, go to local immigration office again to get the last 60 days stamp.

You will need to do the extension twice. (TM 30+work permit+reports+ 1900=30 day and 60 days.)

Before you do it the second last time, you also need to send report of your work and a report of you organization to local government. My place of work is in ChiangMai Province. Therefore, my reports went to the provincial government of ChiangMai. Before the end of ninth month, it will notify the immigration office if they are ok with you. If you do, at the end of ninth month, you will get a one year stamp.

you would apply for an extension of stay at the local immigration office based on documentation from the place you volunteer at. Once you get your extension your son would apply for an extension that matches yours because they are a dependent of someone on a long term extension.