I'm just wondering if I arrive on a single entry non 'o' (due to having a Thai son) would it be possible to get a 60 day extension at immigration without taking my son with me as I don't really want to take him out of school. 

Immigration will certainly want him to be with you.

Plan the trip to immigration in the afternoon so he does not miss a full day of school.

Thanks for the quick reply. Also would the Thai embassy in London, issue a multi entry non 'o' without showing a bank statement? I have full custody of my son, which is stated on my divorce papers

5 minutes ago, somewhereinengland said:

Thanks for the quick reply. Also would the Thai embassy in London, issue a multi entry non 'o' without showing a bank statement? I have full custody of my son, which is stated on my divorce papers

Yes they will issue one without financial proof.

Thanks again, so I just need a copies of my sons, Thai birth certificate, passport, and tabbiban?

7 minutes ago, somewhereinengland said:

Thanks again, so I just need a copies of my sons, Thai birth certificate, passport, and tabbiban?

For the 60 day extension there is no need for the passport. You will also need proof of residence such as a rental agreement.

For the visa the passport will be accepted but not an actual requirement.

Sorry I meant for the visa. Do I need to summit my divorce papers too?

17 minutes ago, somewhereinengland said:

Sorry I meant for the visa. Do I need to summit my divorce papers too?

Although it may not be a requirement attaching a copy of it would not hurt.

Thanks a lot

2 hours ago, somewhereinengland said:

I'm just wondering if I arrive on a single entry non 'o' (due to having a Thai son) would it be possible to get a 60 day extension at immigration without taking my son with me as I don't really want to take him out of school. 

Probably not, but it's not a hard and fast rule. They can issue the extension without him there if they choose to. I wouldn't make the trip, unless local, without asking the office first. If you were to try then a letter from the school in support might swing it.