What should I do about my exit flight from Thailand if my return is after the 60-day visa-free stay?

It's complicated.

Arriving in Thailand next week with my Thai lady.

Our UK return flights are scheduled for 3 months after our arrival.

1. Might I have issues (not being a Thai resident) in that my return flight is more than the 60 days automatic visa free stay period for UK nationals? I've been advised *by friends and acquaintances) everything from "forget about it, there'll be no problems" to "better book a flight out of Thailand before the 60 days, even if you don't use it" and "just book a bus to Vietnam during the 60 day period even if you don't use it".

1. It GETS WORSE in that I will actually leave Thailand by (aroundabouts) the 60 days (as yet unscheduled business appointments to keep in the UK) but will be booking flights from LOS to the UK and back, once the dates I must be back in the UK are confirmed, so that me and my Thai lass can return back to the UK together, as per the already scheduled flight.

1. When I return to Thailand, having been away as advised, should I go through immigration as a new arrival or do I need to go to the visa extension desk?

I hope that little lot is a little clear than appears, at first reading.

Any advice gratefully received.

Thank you.