If they haven't been registered or used and the design hasn't changed then really they are still new. Tires and battery may have deteriorated slightly but otherwise...
To start my small Stihl I would lock the throttle in the start position using the push button. Give it one pull on choke then release the choke and start. If it didn't then I would apply the choke and start the procedure again.
With electronic ignition they need a minimum amount of RPM to generate a spark. So you need to use explosive pulls. As we get a lot older that becomes harder.
Make sure you gave them a number of a Thai speaker if you live in an unusual place.
Usually they tell you on the day they deliver and sometimes you get the deliverer's phone number.
I'm using Kawasaki Vent vert 10-50. It is green and crystal clear. You could bung some of that in and see if it changes colour. It would be very easy to see any change.
Battle Of Britain Michael Cain, Golf Clubs, flying club grass field,
"The Germans won't go there"
"I'm not surprised. Have you seen it?"
"tents and flies"