I understand if the guest returns from a visa run, having crossed the border and left Thailand, then a new TM30 will have to be submitted.

 

But what about the guest obtaining a 30-day extension after paying 1,900 baht at the Immigration Office ?  Must a new TM30 be submitted ?

 

For example, on the 1st TM30 informed that the guest would stay for 60 days.  However, the guest merely had a visa exemption stamp for 30 days.  So is it necessary then to submit a 2nd TM30 after another 30-day extension is obtained?

When you come in visa exempt you can do a TM30 with period of stay up to the exit date of your entry stamp (30 days). You can then apply for a 30 day extension (one time per entry) with a copy of that TM30, you don't have to apply for another TM30 to cover the extra 30 days of the extension

 

6 hours ago, thairookie said:

For example, on the 1st TM30 informed that the guest would stay for 60 days.  However, the guest merely had a visa exemption stamp for 30 days.  So is it necessary then to submit a 2nd TM30 after another 30-day extension is obtained?

Not necessary in this case. However, a new visa exempt entry (or an entry with a new visa) does necessitate a new notification.

1 hour ago, BritTim said:

However, a new visa exempt entry (or an entry with a new visa) does necessitate a new notification.

Pretty sure OP's opening sentence says he knows this already 😉

 

"I understand if the guest returns from a visa run, having crossed the border and left Thailand, then a new TM30 will have to be submitted."