So....here's one to throw out there. If he gets an extension I'm thinking technically he will also have to do a 90 day report? And, depending on where he resides, make sure he has filed a TM30 or he may be fined.
Wild... didn't know you could do it after expiry. I did mine about a month before without anyone saying anything. BTW, length of the renewal validity is dependant on visa. If you happen to be on a tourist visa at the time, they'll only give you two years.
You will have no problem. The whole point of the VEE is so that people can fly around the region, in and out of Thailand and not need a visa.
If you had a tourist visa, that would not help because as soon as you leave the country, the single entry visa is no longer valid (unless you buy a re-entry permit). But again, no need to do this.
The reason they say visa exempt entries are limited is because 1) you can only do two land based visa exempt entries per year and 2) people who have been doing visa exempt entries for months and months (even years) have a high probability of being stopped by immigration and having to show things like money, onward flights, hotel reservations, etc. In your instance, you are only in the region for a month. Immigration will have no concerns with you. Technically, they can ask that you show you have 10,000 baht (or equivalent foreign currency) when you enter on exempt entry but again, you're not a frequent/long term visitor to Thailand so you'll be fine. Enjoy your travels!
Actually, scratch that... NY embassy requires the same $7000. But they do seem to be more lax on the flight requirements.
If you can't meet the requirements, you'll have to go with other visa options (SETV for 60 days, extend at local immigration +30 days for 1900 baht, then go to a neighbouring country (i.e. Laos) and apply for a new SETV).