60 day Entry Extension or Border Run

Hi, 

Quick and, hopefully, simple question.

1) I'm on a Single Entry non-o 90 days visa on basis of Thai child. 

Am thinking about getting a 60 day extension. I've read online that the child has to be present at immigration. Is this the case at Chang Wattana? My son is at boarding school and will be a headache to pull him out for one day just to do this.  I have the birth certificate original.

 2) Alternatively, I'm thinking of maybe just doing a border run across land. I haven't had a Visa exempt stamp in years and was wondering if I'd be issued a 30-day stamp on returning as was the case in the old days? I remember it switched to 15 days at one point. 

I'm not looking at a long-term visa as I am working abroad next month, just looking at the simplest way to give myself another month in-country. 

Thanks so much for any comments/advice! 

GFL